A pin against the king is called absolute since the pinned piece cannot legally move out of the line of attack (as moving it would expose the king to check).[1] Cf. relative pin.
active
Describes a piece that threatens a number of squares, or that has a number of squares available for its next move. It may also describe an aggressive style of play.[2] Antonym: passive.
Suspension of a chess game with the intention to finish it later. It was once very common in high-level competition, often occurring soon after the first time control, but has been mostly abandoned due to the advent of computer analysis.[3] See also sealed move.
adjudication
A way to decide the result of an unfinished game. A tournament director, or an impartial and strong player, will evaluate the final position and assign a win, draw, or loss assuming best play by both players.[4]
adjust
See touch-move rule. To adjust the position of a piece on its square without being required to move it. A player may do this only on their turn, and must first say "I adjust", or the French equivalent "J'adoube".[5]
advanced pawn
A pawn that is on the opponent's half of the board (the fifth rank or higher for White; the fourth rank or lower for Black). An advanced pawn may be weak if it is overextended, lacking support and difficult to defend, or strong if it cramps the enemy by limiting mobility. An advanced passed pawn that threatens to promote can be especially strong.[6]
advantage
A better position with the chance of winning the game. Evaluation factors can include space, time, material, and threats.[2]
The standard way to record the moves of a chess game, using alphanumeric coordinates for the squares.[8] Also called standard notation.[9] Abbr. AN.
amateur
Any player whose main occupation is not chess.[10] The distinction between professional and amateur is not very important in chess as amateurs may win prizes, accept appearance fees, and earn any title, including World Champion.[10][11] In the 19th century, "Amateur" was sometimes used in published game scores to conceal the name of the losing player in a Master vs. Amateur contest. It was thought to be impolite to use a player's name without permission, and the professional did not want to risk losing a customer.[11] See also NN.
analysis
The study of a game or a position, in order to evaluate the quality of the moves and various other aspects of the game or position. At the end of a game, the players will often do an analysis of the game. See also post-mortem.[2]
A practice, common in the 19th century, whereby a player would announce a sequence of moves, believed by them to constitute best play by both sides, that led to a forced checkmate for the announcing player in a specified number of moves (for example, "mate in five").[12]
antipositional
A move or a plan that is not in accordance with the principles of positional play.[13] Antipositional is used to describe moves that are part of an incorrect plan rather than a mistake made when trying to follow a correct plan. Antipositional moves are often pawn moves; since pawns cannot move backwards to return to squares they have left, their advance can create irreparable weaknesses.[14]
Anti-Sicilian
An openingvariation that White uses against the Sicilian Defense (1.e4 c5) other than the most common plan of 2.Nf3 followed by 3.d4 cxd4 4.Nxd4 (the Open Sicilian). Some Anti-Sicilians include the Alapin Variation (2.c3), Moscow Variation (2.Nf3 d6 3.Bb5+), Rossolimo Variation (2.Nf3 Nc6 3.Bb5), Grand Prix Attack (2.Nc3 Nc6 3.f4 g6 4.Nf3 Bg7 and now 5.Bc4 or 5.Bb5), Closed Sicilian (2.Nc3 followed by g3 and Bg2), Smith–Morra Gambit (2.d4 cxd4 3.c3), and Wing Gambit (2.b4).[15]
A game that is guaranteed to produce a decisive result, because if there is a draw it is ruled a victory for Black. In compensation for this White is given more time on the clock. Often White is given five minutes, and Black four. This format is typically used in playoff tiebreakers when shorter blitz games have not resolved the tie.[18]
A type of decoy involving a sacrifice of a minor or major piece on a square next to the enemy king, forcing the king to abandon the defense of another square. For example (see diagram), the black queen has interposed to block a check from the white queen, and White can check the king from the opposite direction to win the queen.[21]
An automaton is a self-operating machine. In chess, it refers to chess-playing machines that were in fact hoaxes and under the control of hidden human players. Automatons stirred up great interest in the 18th and 19th centuries and inspired early thoughts of the possibility of artificial intelligence. By far, the most famous chess-playing "automaton" was The Turk, whose secret of human control was kept for a very long time. The first true automaton El Ajedrecista was created by Leonardo Torres y Quevedo.
Symbol used for the bishop when recording chess moves in English.[22]
back rank
A player's first rank (the rank on which the pieces stand in the starting position). White's back rank is Black's eighth rank; Black's back rank is White's eighth rank.[23] Also called home rank and first rank.
A checkmate delivered by a rook or queen along a back rank from which the mated king is unable to move because it is blocked by friendly pieces (usually pawns) or squares under attack on the player's second rank.[23] Also called back-row mate.
back-rank weakness
A situation in which a player is under threat of a back-rank mate and, having no time/option to create an escape for the king, must constantly watch and defend against that threat, for example by keeping a rook on the back rank.[23]
A position in which a king is the only man of its color on the board.[26]
Basque chess
Or Basque system. A chess competition in which the players simultaneously play each other two games on two boards, each playing White on one and Black on the other. There is a clock at both boards. It removes the bonus in mini-matches of playing White first. Basque chess was first played in the 2012 Donostia Chess Festival in the Basque Country, Spain.[27]
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A pair of white rooks are aligned along their battery, ready to do some action.
Gathering pieces along a line of action in somewhat varying setups. In games, it usually means to line up rooks and/or the queen on a file, or to place a bishop and a queen on a diagonal.[20] In chess problems, battery refers to an arrangement of two pieces in line with the enemy king on a rank, file, or diagonal so that if the middle piece moves a discovered check (or a threat other than a check) will be delivered.[28] See also Alekhine's gun.
An abbreviation for the British Chess Magazine.[30]
BCO
An abbreviation for the 1982 openings reference book Batsford Chess Openings, by Raymond Keene and Garry Kasparov. The second edition (1989) is often called BCO-2.[31] Cf. ECO and MCO.
best play
The theoretical absolute and ideal best moves from any given position.[32]
Charousek vs. Maroczy, 1895
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Example of a "big pawn": the white bishop is doing the work of a pawn and has no bigger prospects.
big pawn
A bad bishop stuck behind its own pawns and defending them—effectively doing the work of a pawn.[33]
bind
A strong grip or stranglehold on a position that is difficult for the opponent to break. A bind is usually an advantage in space created by advanced pawns. The Maróczy Bind is a well-known example.[34] See also squeeze.
A piece that may move along diagonals without jumping.
bishop pair
The player with two bishops is said to have the bishop pair. Two bishops are able to control the diagonals of both colors. In open positions, two bishops are considered to have an advantage over two knights, or a knight and a bishop.[20] Also called the two bishops.
bishop pawn
Or bishop's pawn. A pawn on the bishop's file, i.e. the c-file or f-file. Sometimes abbreviated "BP".[35]
bishops on opposite colors
Or bishops of opposite colors. A situation in which one player has only a light-square bishop remaining while the other has only a dark-square bishop remaining. In endgames, this often results in a draw if there are no other pieces than pawns, even if one side has a material advantage of one, two or even three pawns, since the bishops control different squares (see Opposite-colored bishops endgame). In the middlegame, however, the presence of opposite-colored bishops imbalances the game and can lead to mating attacks, since each bishop attacks squares that cannot be covered by the other.[36]
black
The dark-colored squares on the chessboard are often referred to as "the black squares" even though they are often some other dark color. Similarly, "the black pieces" are sometimes actually some other (usually dark) color.[37] See also white.
The designation for the player who moves second, even though the pieces ("the black pieces") are sometimes actually some other (usually dark) color.[38] See also White and first-move advantage.
A form of chess in which one or both players are not allowed to see the board.[39]
blind pigs
A pair of rooks on the opponent's second rank are referred to as "pigs" as they tend to devour pawns and pieces, and "blind pigs" if they cannot find the mate.[40]
[from German: Blitz, "lightning"] A fast form of chess with a very short time limit, usually three or five minutes per player for the entire game. With the advent of electronic chess clocks, the time remaining is often incremented by one or two seconds per move.[41]
Black has a solid light-square blockade. White's bishop cannot challenge Black's minor pieces.
blockade
The placement of a piece directly in front of an enemy pawn, where it obstructs the pawn's advance, and hinders the movements of the other enemy pieces. The enemy pawn provides some shelter to the piece that is blocking it, thereby protecting it from attacks by enemy pieces. A blockade is most effective against passed or isolated pawns. The ideal piece to use as a blockader is the knight. This strategy was famously formulated by Aron Nimzowitsch in 1924.[44][45]
blocked position
A position where both sides are constrained from making progress, typically by interlocking pawn chain(s) dividing the available space into two camps.[46] See also closed game.
Boden's Mate, named for Samuel Boden, is a checkmate pattern in which the king, usually having castled queenside, is checkmated by two crisscrossing bishops. Immediately prior to delivering the mate, the winning side typically plays a queen sacrifice on c3 or c6 to set up the mating position.[47]
An opening move found in standard reference books on opening theory. A game is said to be "in book" when both players are playing moves found in the opening references. A game is said to be "out of book" when the players have reached the end of the variations analyzed in the opening books, or if one of the players deviates with a novelty (or a blunder).[49]
A move that gains space and therefore freedom of movement, or the opening of a blocked position by the advance or capture of a pawn.[51] See also pawn break.
breakthrough
Penetration of the opponent's position, or destruction of the defense, often by means of a sacrifice.[20]
A time control method with time delay, invented by David Bronstein. When it becomes a player's turn to move, the clock waits for the delay period before starting to subtract from the player's remaining time.[53]
A tournament round in which a player does not have a game, usually because there are an odd number of players. A bye is normally scored as a win (1 point), although in some tournaments a player is permitted to choose to take a bye (usually in the first or last round) and score it as a draw (½ point).[58]
A tournament organised by the FIDE, the third and last qualifying cycle of the World Chess Championship. The participants are the top players of the Interzonal tournament plus possibly other players selected on the basis of rating or performance in the previous candidates tournament. The top ranking player(s) qualify(ies) for the world championship.[63]
can opener
[colloq.] The plan of attacking a kingside position (sometimes a fianchettoed one) by advancing the h-pawn with the intention of opening a file near the defender's king.[64][verification needed]
capped piece
A particular piece with which one player attempts to deliver checkmate. The requirement to checkmate with the capped piece constitutes a handicap. When the capped piece is a pawn, it is called a pion coiffé [from French, "capped pawn"].[65]
capture
A move by a pawn or piece that removes from the board the opponent's pawn or piece. The capturing piece then occupies the square of the captured piece, except in the case of a capture that is done en passant.[66]
A move in which the king and a rook are moved at the same time. It moves the king from the center to a flank where it usually is safer, and it develops the rook. It is the only time two pieces are moved in a turn. Castling can be done on either the kingside (notated 0-0) or the queenside (0-0-0). Castling cannot be done in reply to a check, nor if the king were to cross or land on a square which is under attack by the opponent, nor if either the king or the rook involved has already moved.[67][68]
castling into it
A situation where one side castles and a result is that the king is in more danger at the destination than on the initial square, either immediately or because lines and diagonals can be more readily opened against it.[69]
The category of a tournament is a measure of its strength based on the average FIDE rating of the participants. The category is calculated by rounding up the number: (average rating − 2250) ÷ 25. So each category covers a 25-point rating range, starting with Category1 which spans ratings between 2251 and 2275. A Category 18 tournament has an average rating between 2676 and 2700.[71]
Or centre. The four squares in the middle of the board.[72] See also expanded center. Sometimes short for pawn center. A king "in the center" can refer to an uncastled king on a center file.
center file
Or centre file. The king's file (e-file) or queen's file (d-file).
center pawn
Or centre pawn. A pawn on the king's file (e-file) or queen's file (d-file).[73]
centipawn
A unit of evaluation used by chess engines, e.g. an evaluation of +1.32 is worth 20 centipawns more than an evaluation of +1.12. Historically a centipawn corresponded to a material value of 0.01 of a pawn; however, the strongest modern engines no longer rate pawns as worth 1.[74]
Moving a piece or pieces toward the center of the board, where they will not only control the center, but also extend their influence to other areas. Pieces are best placed near the center of the board, because they increase their power and maneuverability. Knights in particular benefit from being centralized.[75] Antonym: decentralization.[76]
A direct attack on the king by an enemy man. The attacked king is said to be in check. There are only three possible immediate responses to a check: capturing the attacking piece, moving the king to an unattacked square, or interposing a piece between the attacker and the king. In casual games a player usually announces "check"; however, this is not a requirement in tournament games.[78]
Often shortened to mate. A position in which a player's king is in check and the player has no legal move (i.e. cannot move out of or escape the check). A player whose king is checkmated loses the game.[79]
The failure of a player to see a good move or danger that should normally be considered obvious. The term was coined by Siegbert Tarrasch. Similar to Kotov syndrome.[80]
A device made up of two adjacent clocks and buttons, keeping track of the total time each player takes for their moves. Immediately after moving, the player hits their button, which simultaneously stops their clock and starts their opponent's. The picture shown displays an analogue clock where the term flag fall originates. Modern clocks are digital.[82]
Removal of piece from a square, rank, file or diagonal so that another piece may use it. It often involves sacrificing the piece that blocked the position.[87] See Clearance sacrifice.
clock move
In a game played clock move, a move is considered completed only after the clock is pressed. For example, one could touch a piece, then move a different piece—as long as the player has not pressed their clock button. This way of playing is uncommon but can be seen in casual games or blitz games.[88]
A file on which White and Black each have a pawn.[90]
closed game
Or close game. A closed game has few open lines (files or diagonals). It is generally characterized by interlocking pawn chains, cramped positions with few opportunities to exchange, and extensive maneuvering behind lines. Such a game may evolve and later become an open game.[91] Cf. open game. See also positional play.
A Closed Game is a particular opening that begins with the moves 1.d4 d5. It is also known as a Double Queen's Pawn Opening or Double Queen's Pawn Game.[92] See also Open Game and Semi-Open Game.
closed tournament
A tournament in which only invited or qualifying players may participate. Also called invitational tournament. Cf. open tournament.
Adjective used to describe a move, player, or style of play characterized by risky, positionally dubious play that sets traps for the opponent. The name comes from the notion that one would expect to see such play in skittles games played in a coffeehouse or similar setting, particularly in games played for stakes or blitz chess. The Blackburne Shilling Gambit is a typical example of coffeehouse play.[93]
color
Or colour. The white or black pieces, and the white or black squares. The actual pieces and squares may be other colors, usually light and dark, but they are referred to as white and black.[83] See White and Black in chess.
colorbound
Or colourbound. The property of a piece to access only squares of one color. In standard chess, each bishop is colorbound to either the white or black squares.
colors reversed
Or colours reversed. With colors reversed refers to opening moves by White normally played by Black, or vice versa. An example is the King's Indian Attack, where White's opening setup mirrors Black's setup in the King's Indian Defense. In such openings, White necessarily has an extra tempo compared to Black. Also called a reverse opening.[94]
That which is gained in return for a loss – often a positional improvement in return for loss of material. If material is sacrificed there may be a gain in development, or if a minor piece is exchanged for two or three pawns, the pawns would be the compensation.[95]
computer move
A move that seems likely to have been played by a computer rather than a human, either because the move seems counterintuitive, or to not make immediate sense, or to eventually make sense but not until deep into the game. Computer moves seem to be what they are: moves based on millions of brute-force calculations, and not on intuition, aesthetics, or emotion. A computer move would overlook a dramatic capture that might cause an opponent to immediately resign, in favor of an obscure move that may turn out to be only slightly better. At one time the term was used disparagingly, but its meaning has evolved as computers have improved. It is occasionally used to suggest that a player has been assisted by computer.[96][97]
Passed pawns on adjacent files. These are considered to be unusually powerful (often worth a minor piece or rook if on the sixth rank or above and not properly blockaded) because they can advance together.[72] See also connected pawns.
Two rooks of the same color on the same rank or file with no pawns or pieces between them. Connected rooks are usually desirable. Players often connect rooks on their own first rank or along an open file.[98] See also doubled rooks.
consolidation
The improvement of a player's position by the reposition of one or more pieces to better square(s), typically after a player's attack or combination has left their pieces in poor positions or uncoordinated.[99]
consultation game
A game in which two or more players consult with each other to jointly decide the moves for one side. Consultation games may also involve teams of two or more players playing on both sides.[100]
When a player's pawn, piece or pieces guard a square, or squares, or a file, or a rank in such a way that the territory can be advantageously used; and the opponent is prevented from using the territory.[101] Also, the player that has the initiative has control.
Chess played at a long time control by long-distance correspondence. Traditionally correspondence chess was played though the post; today it is usually played over a correspondence chess server or by email. Typically, one move is transmitted in every correspondence.[105]
Corresponding squares are pairs of squares such that when a king moves to one square, it forces the opponent's king to occupy the other square in order to hold the position. Corresponding squares usually occur in pawn endgames. The theory of corresponding squares has developed to include complex calculations based on math-like formulas.[106] Also called related squares. Cf. opposition.
counterattack
An attack that responds to an attack by the opponent.[107]
A gambit offered by Black, for example the Greco Counter Gambit, usually called the Latvian Gambit today (1.e4 e5 2.Nf3 f5?!); the Albin Countergambit (1.d4 d5 2.c4 e5); and the Falkbeer Countergambit (1.e4 e5 2.f4 d5). An opening need not have "countergambit" in its name to be one, for instance the Benko Gambit (1.d4 Nf6 2.c4 c5 3.d5 b5); the Englund Gambit (1.d4 e5?!); the Budapest Gambit (1.d4 Nf6 2.c4 e5); the Blackburne Shilling Gambit (1.e4 e5 2.Nf3 Nc6 3.Bc4 Nd4?!); and many lines of the Two Knights Defense (e.g. 1.e4 e5 2.Nf3 Nc6 3.Bc4 Nf6 4.Ng5 and now 4...Bc5!? [the Wilkes–Barre Variation or Traxler Counterattack]; 4...Nxe4?!; 4...d5 5.exd5 Na5 6.Bb5+ c6 [the main line]; 4...d5 5.exd5 Nd4 [the Fritz Variation]; and 4...d5 5.exd5 b5 [the Ulvestad Variation]) are all examples of countergambits.[108]
A disparaging term for a move considered unsophisticated, especially an unnecessary single-step advance of the rook's pawn in the opening. The term was popular in London in the late 19th century.[110]
The moment in a game or opening when the evaluation shows that things are about to change, either towards an advantage for one player, or towards equality; a wrong move can be disastrous.[109]
A cross-check is a check played in reply to a check, especially when the original check is blocked by a piece that itself either delivers check or reveals a discovered check from another piece.[112]
crosstable
An arrangement of the results of every game in a tournament in tabular form. The names of the players run down the left side of the table in numbered rows. The names may be listed in order of results, alphabetically, or in pairing order, but results order is most common. There may be one column for each successive round, or, in a round-robin tournament, there may be one column for each player, with the players in the same order in the columns as in the rows. For each player, the table cells on the player's row record the results of the player's games, using 1for a win, 0for a loss, and ½ for a draw. (In a double round-robin tournament each cell contains two entries, as each pair of players plays two games alternating White and Black.)[113] For examples see Hastings 1895 chess tournament, Nottingham 1936 chess tournament, and AVRO tournament.
crush
Slang for a quick win, especially an overwhelming attack versus poor defensive play. A crushing move is a decisive one.
The 32 dark-colored squares on the chessboard, such as a1 and h8. A dark square is always located at a player's left-hand corner.[38] Cf. light squares.
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A dead draw by means of insufficient material. King versus king and bishop will never lead to checkmate. If for Black, a knight or a light-squared bishop were added to the position (e.g. a Nf3 or Bf3), a mate would be possible in theory for either side, but not with reasonable play, making it a "dead draw" in the broader sense.
dead draw
A drawn position in which neither player has any realistic chance to win. In the strict sense, dead draw may refer to a position in which it is impossible for either player to win (such as insufficient material). In a broader sense, it may refer to a simple, lifeless position that would require a major blunder before either side would have a chance to win.[114]
A position where neither player can mate the opponent's king with any series of legal moves (e.g. knight and king against a bare king). This position is drawn.[116]
A decoy tactic that involves luring an enemy piece away from a good square; typically, away from a square on which it defends another piece or threat. Deflection is thus closely related to overloading.[119] See also attraction.
demonstration board
A large standing chess board used to analyze a game or show a game in progress. Johann Löwenthal invented the demonstration board in 1857.[120]
A system of recording chess moves, used primarily in the English and Spanish speaking countries until the 1980s. Descriptive notation is based on natural language descriptions of chess moves rendered in abbreviated form, for example "pawn to queen's bishop's fourth" is rendered as "P-QB4". Now replaced by the standard algebraic notation.[121]
A piece that seems determined to give itself up, typically to bring about stalemate or perpetual check. Also an en prise or trapped piece that sacrifices itself for the maximum compensation possible.[122]
development
The movement of non-pawn pieces in the opening from their original squares to squares where they can be more active. Development of one's pieces is one of the objectives of the opening phase of the game.[117]
diagonal
A line of squares of the same color touching corner to corner, along which a queen or bishop can move.[123]
A discovered attack to the king. This occurs when a player moves a piece, resulting in another piece putting their opponent's king in check.[124][125][126]
Two attacks made with one move: these attacks may be made by the same piece (in which case it is a fork); or by different pieces, for example in a discovered attack when the moved piece also makes a threat.[117]
A check delivered by two pieces at the same time. A double check necessarily involves a discovered check. By its nature a double check cannot be met by interposing a defending piece in the line of attack, or by capturing an attacker; when subjected to a double check, the attacked king must move, which makes the double check especially powerful as an attacking tactic.[129]
Two pawns of the same color on the same file; generally considered a weakness due to their inability to defend each other.[123]
doubled rooks
A powerful configuration in which a player's two rooks are placed on the same file or rank with no other men between them. They defend each other and attack along the shared file or rank, as well as two additional ranks or files. The configuration can be especially decisive in the endgame.[130]
A game that ends without victory for either player. Most drawn games are draws by agreement. The other ways that a game can end in a draw are by stalemate, by a dead position, by the threefold repetition rule, by the fifty-move rule, by the fivefold repetition rule and by the seventy-five-move rule. A position is said to be a draw (or a "drawn position" or "theoretical draw") if either player can, through correct play, eventually force the game into a position where the game must end in a draw, regardless of the moves made by the other player. A draw is usually scored as ½ point, although in some matches only wins are counted and draws are ignored.[117]
A game that is ended by both players' accepting a draw.[132] See also resign.
draw death
Hypothetical scenario whereby elite-level chess players, aided by modern computer analysis, become so good that they never make mistakes, leading to endless drawn games (since chess is widely believed to be drawn with best play from both sides).[133]
A style of play in which the activity of the pieces is favored over more positional considerations, even to the point of accepting permanent structural or spatial weaknesses. Dynamism stemmed from the teachings of the Hypermodern school and challenged the dogma found in more classical teachings, such as those put forward by Wilhelm Steinitz and Siegbert Tarrasch.[139]
The English Chess Federation (ECF) is the governing chess organisation in England and is one of the federations of the FIDE. It was known as the British Chess Federation (BCF) until 2005 when it was renamed.
The Encyclopaedia of Chess Openings (ECO), a standard and comprehensive chess opening reference. Also a classification system (ECOcode) for openings that assigns an alphanumeric code from A00 to E99 to each opening.
The Elo rating system is a method for calculating the relative skill levels of chess players, named after Arpad Elo. Since 2012, FIDE publishes a monthly international chess rating list using the Elo system.[143]
A computerized database of endgames with a small number of pieces, providing perfect play for both players, and thus completely solving those endgames. As of 2012, tablebases have been calculated for all positions with up to seven pieces.[144]
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After 1.d4 c5 2.d5 e5, White can play 3.dxe6, capturing the e-pawn en passant on the next move. The white pawn is placed on e6, and the black pawn on e5 is removed from the board.
[from French, "in the act of passing"] The rule that allows a pawn that has just advanced two squares to be captured by an enemy pawn that is on the same rank and adjacent file. The pawn can be taken as if it had advanced only one square. Capturing en passant is possible only on the next move.[145] Abbr. e.p.
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The pawn on e4 is en prise.
en prise
[from French, "in a position to be taken",[146][147] often italicized] En prise describes a piece or pawn exposed to a material-winning capture by the opponent. This is either a hanging piece, an undefended pawn, a piece attacked by a less valuable attacker, or a piece or pawn defended insufficiently. For instance, 1.e4 Nf6 2.Nf3? leaves White's e-pawn en prise.[148][149]
Or equalise. To reach a position where the players have equal chances of winning, referred to as equality, or a position that is equal. In the opening, because White has the advantage of the first move, the immediate goal for Black is to achieve equality.[151]
Or simply eval. The analysis of a position. A computer or engine evaluation is a means of assigning a number value to a position, based not on intelligence, but on algorithms, which vary from engine to engine and depend on engine strength. Engine evaluations have foibles and imperfections even when functioning as designed. If an engine describes a position as +2.50, the plus sign ("+") indicates the position is favorable to White; a minus sign ("−") indicates the position is favorable to Black. The number can correspond to the approximate value of pieces, although engines use other factors besides material. The notation +2.50 indicates that White is ahead by two and one-half pawns. The notation +M4 (or sometimes #4) indicates that White can force checkmate in four moves.[152][153][154] Cf. analysis.
To swap or trade pieces by capture. Usually the pieces are of equal value (i.e., rook for rook, knight for knight, etc.), or of bishop for knight (two pieces that are considered approximately equal in value).[155] Also called even exchange.
The advantage of a rook over a minor piece (knight or bishop). The player who captures a rook for a minor piece is said to have "won the exchange", the player who has lost the rook has "lost the exchange". An exchange sacrifice is giving up a rook for a minor piece.[148]
This is a type of opening in which there is an early, voluntary exchange of pawns or pieces.[156]
exhibition
Chess games played for the public in various formats and for various purposes, often to promote the game, or a particular match or player, or as a fundraiser. An exhibition may pit two masters against each other, and normally use chess clocks. In a simultaneous exhibition, one player takes on a number of opponents at once, and it is often not timed. A blindfold exhibition is the same but more challenging, since the exhibitor plays without seeing the boards.[157]
A Forsyth–Edwards Notation derivative format that contains the position on the chessboard, but not the game. It is primarily used to test chess engines.[160] Abbr. EPD.
To develop a bishop to the board's longest diagonal on the file of the adjacent knight (b2 or g2 for White; b7 or g7 for Black). The fianchetto of both bishops by a player is called a double fianchetto. Less common is to develop a bishop to the rook's file (a3 or h3 for White; a6 or h6 for Black), called extended fianchetto.[131] The Italian word ("little flank") is pronounced /ˌfiənˈkɛtoʊ/ or /ˌfiənˈtʃɛtoʊ/ in English, while its name sounds like [fjaŋˈketto] in Italian.[163][164]
FICGS Grandmaster
A correspondence chess title calculated by the FICGS (Free Internet Correspondence Games Server) organization.[165]
The World Chess Federation (Fédération Internationale des Échecs), the primary international chess organizing and governing body. The abbreviated name FIDE is nearly always used in place of the full name in French.[166]
A draw may be claimed if no capture or pawn move has occurred in the last fifty moves by either side.[168] For the occurrence of seventy-five such moves, see seventy-five-move rule.
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The f-file
file
A column of the chessboard. A specific file can be named either using its position in algebraic notation, a–h, or by using its position in descriptive notation. For example, "f-file" and "king bishop file" both denote the squares f1–f8 (or KB1–KB8 in descriptive notation).[166]
fingerfehler
[from German, "finger mistake"] An error caused by unthinkingly touching the wrong piece or releasing a piece on the wrong square, forcing the player to move that piece in accordance with the touch-move rule.[169]
first board
In team chess, the player who is assigned to face the strongest opponents. Also called top board and board one. Second board faces the next strongest players, followed by third board, and so on. Generally board assignments must be made before the competition begins and players may not switch boards, although reserve players are often allowed as substitutes.
Also known as Chess960. A variation of chess invented and advocated by Bobby Fischer. The pieces and pawns have their normal moves, but the setup of pieces on the first rank is random, except that two rules must be followed: the king must be placed on a square between the rooks, and the bishops are placed on squares of opposite color. Black's pieces are placed opposite White's. Castling may be done; the special castling rules incorporate the normal castling in classic chess.[170][171]
Fischer delay
A time control method with time delay, invented by Bobby Fischer. When it becomes a player's turn to move, the delay is added to the player's remaining time.[172]
fish
[derogatory slang] A weak or easily defeated player or players. See also woodpusher.
Part of an analogue chess clock, usually red, that indicates when the minute hand passes the hour. To "flag" someone means winning the game on the basis of the opponent exceeding the time control.[166]
flag-fall
The event when the allotted time of a player has just expired; the player has run out of time.[115]
flank
The queenside a-, b-, and c-files; or the kingside f-, g-, and h-files. Distinguished from the center d-file and e-file.[174] Also called wing.
The shortest possible chess game ending in mate: 1.f3 e5 2.g4 Qh4# (or minor variations on this).[176]
forced mate
A sequence of two or more moves culminating in checkmate that the opponent cannot prevent.[177]
forced move
A move that is the only one to not result in a serious disadvantage for the moving player. Forced can also be used to describe a sequence of moves for which the player has no viable alternative, for example "the forced win of a piece" or "a forced checkmate". In these cases the player cannot avoid the loss of a piece or checkmate, respectively.[176] Cf. forcing move.
A simultaneous attack by a single piece on two (or more) of the opponent's pieces (or other direct target, such as a mate threat). When the attacker is a knight the tactic is often specifically called a knight fork. Some sources state that only a knight can give a fork and that the term double attack is correct when another piece is involved, but this usage is rare.[5]
A standard notation for describing a particular board position of a chess game. The purpose of FEN notation is to provide all the necessary information to restart a game from a particular position.[180][181] Abbr. FEN.
In endgame theory, a fortress is an impenetrable position which, if obtained by the side with a material disadvantage, may result in a draw due to the stronger side's inability to make progress.[182]
frame
A square region of the board enclosing another region not part of the given frame, akin to a picture frame. Also referred to as a ring.[183] The outer frame consists of the 28 squares along the edge of the board, the middle frame consists of the 20 squares just inside the outer frame, and the inner frame consists of the 12 squares just inside the middle frame.[184] The notion of the frame may be expanded to include the center itself as the innermost frame. The mobility of pieces is closely related to the frame on which they stand. In general, a piece closer to the center has greater freedom of movement than a piece closer to the edge of the board.
friendly game
A game that is not played as part of a match, tournament, or exhibition. Often the game is not timed, but if a chess clock is used, rapid time controls are common. The term refers only to the circumstances in which the game is played, not the relationship between the players or the intensity of the competition.[185] Also called casual game and informal game.
frontier line
An imaginary line dividing the board into two halves, passing between the fourth and fifth ranks.[186][187] The frontier line separates White's side of the board from Black's side. Coined by Nimzowitsch.[188][189]
[from French: gardez la reine!, "Protect the Queen!"] An announcement to the opponent that their queen is under direct attack, similar to the announcement of "check". This warning was customary until the early 20th century.[191]
The highest title a chess player can attain (besides World Champion). Awarded by FIDE, the title is valid for life unless exceptional circumstances (such as cheating) occur.[195] Abbr. GM.
A game in which the players agree to a quick draw. Originally it referred to such games between grandmasters, but the term can now refer to any such game.[195]
A typical sacrifice of a bishop by White playing Bxh7+ or by Black playing ...Bxh2+ against a castled king to initiate a mating attack. Also known as the classical bishop sacrifice.[196]
A nickname for the h-pawn, sometimes occurring in the expression, "Harry the h-pawn".[198][199]
hauptturnier
German word that is freely translated as "candidates tournament". In the early part of the 20th century, it was necessary for the ambitious European amateur to win a succession of prizes in small tournaments, to progress to a higher level of competition. The creation of the hauptturnier enabled the process to become more formalized, and they became a regular feature of the major German chess congresses. Winning such an event conferred the title of 'Master of the German Chess Federation', and this, in turn, could be used to gain admittance to prestigious international tournaments. Some of the best players in chess history, such as Emanuel Lasker and Siegbert Tarrasch, secured their Master titles and advanced their chess careers in this way.[200]
A square that is inside or near a player's territory that cannot be controlled by a pawn. It is a gap in a player's pawn configuration, and especially dangerous when the hole is close to the center or near the king. A knight landing on a hole may be part of an attack. An example of a hole is e4 in the Stonewall Attack.[201]
home rank
The rank on which the pieces stand in the starting position (rank one for White; rank eight for Black).[202] Also called back rank and first rank.
Horwitz vs. Harrwitz, London 1846, rd. 10, 0–1[203]
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After 30.Qe2. Black's Horwitz bishops are aimed at White's kingside.[204]
Horwitz bishops
A player's light-square and dark-square bishops placed so that they occupy adjacent diagonals, creating a potent attack. Also called raking bishops, and sometimes Harrwitz bishops.[205][206]
human move
A move a human would make, as opposed to the kind of move that only a computer would make.[207]
Hutton pairing
A pairing technique invented in 1921 by George Dickson Hutton for matching teams of players in which only one game is required per player. Has been used regularly for correspondence team events and for matches between many teams conducted on one day.[208] Also called jamboree pairing.
A school of thought that prefers controlling the center with pieces from the flanks as opposed to occupying it directly with pawns. Two major proponents of hypermodernism were Réti and Nimzowitsch.[209] See also classical.
An abbreviation for the older term International Grandmaster. The modern usage is Grandmaster (GM).
illegal move
A move that is not permitted by the rules of chess. An illegal move discovered during the course of a game must be corrected.[211]
illegal position
A position in a game that is a consequence of an illegal move or an incorrect starting position; a position that is impossible to reach by any sequence of legal moves.[211]
Any difference between the positions of White and Black. An imbalanced position is one where White and Black both have unique advantages. Conversely, a balanced position may be drawish.[209]
inaccuracy
A move that is not the best, but not as bad as a blunder.[212]
Refers to the amount of time added to each player's time before each move. For instance, rapid chess might be played with "25 minutes plus 10 second per move increment", meaning that each player starts with 25 minutes on their clock, and this increments by 10 seconds after (or before) each move, usually using the Fischer Delay method.[41] See Time control § Increment and delay methods.
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In the KID Fianchetto Variation (1.d4 Nf6 2.c4 g6 3.Nf3 Bg7 4.g3 0-0 5.Bg2 d6 6.0-0), both sides have Indian bishops.
An opening that begins 1.d4 Nf6. Originally used to describe queen's pawn defenses involving the fianchetto of one or both black bishops; now used to describe all Black defenses after 1.d4 Nf6 that do not transpose into the Queen's Gambit.[214]
The ability to make attacking moves, and force the course of play. It is an aspect of time. The attacking player has the initiative, and the defending player attempts to seize it.[215]
An endgame scenario in which all pawns have been captured, and one side has only its king remaining while the other has only its king, a king plus a knight, or a king plus a bishop. A king plus bishop versus a king plus bishop with the bishops on the same color is also a draw, since neither side can checkmate, regardless of play. Situations where checkmate is possible only if the inferior side blunders are covered by the fifty-move rule.[216] See Draw (chess) § Draws in all games.
The International Correspondence Chess Federation (abbr. ICCF) was founded in 1951 to replace the International Correspondence Chess Association (ICCA).[210]
International Grandmaster
Abbr. IGM. The original name of the FIDE title, now simply called Grandmaster (GM).
An external server that provides the facility to play, discuss, and view chess over the Internet. Abbr. ICS.
interpose
To move a piece between an attacking piece and its target, blocking the line or diagonal of attack. Interposing is not possible if the attacker is a knight, king, or pawn, thus only possible in case of attacking rooks, bishops, or queens. Interposing a piece is one of the three possible responses to a check.[5]
A tournament organised by the FIDE starting from the 1950s to 1993. It was the second qualifying cycle of the World Chess Championship. The participants were selected from the top players of the Zonal tournaments. The top ranking players qualified for the Candidates Tournament. Since 1998 the winners of the zonal tournaments have played short matches against each other over a few weeks in a knockout-style competition to determine who is eligible for the Candidates Tournament.
IQP
An abbreviation for isolated queen pawn. See isolani.
Early 19th-century chess literature classified all openings that did not begin with either 1.e4 e5 or 1.d4 d5 as "irregular". As opening theory developed and many openings previously considered "irregular" became standard (e.g. the Sicilian Defense), the term gradually became less common. Opening books today are more likely to describe debuts such as 1.b4 (the Sokolsky Opening) as "uncommon" or "unorthodox".[217]
A white bishop developed to c4 or a black bishop developed to c5. A bishop so developed is characteristic of the Italian Game. In the Giuoco Piano both players have Italian bishops. The Italian bishop stands in contrast to the Spanish bishop on b5 characteristic of the Ruy Lopez. "Italian" may be used as an adjective for an opening where one or both players have Italian bishops.[220]
(from French, "I adjust", pronounced[ʒa.dub]) The international signal of the intention to adjust the position of a piece on the board. When playing with the touch-move rule, a player must say this in order to be able to touch a piece without being subject to the touched piece rule. The verb adouber, literally "to dub" (raise to the knighthood), is rarely used in contemporary French outside of this context. A local language equivalent, e.g. "I am adjusting", is generally also acceptable.[5]
2. In pawn endings, a square whose occupation by one side's king guarantees the achievement of a certain goal, such as the promotion of a pawn or the win of a pawn.[216]
As a spectator, making comments on a chess game that can be heard by the players. Kibitzing on a serious game while it is in progress (rather than during a post-mortem) is a serious breach of chess etiquette.[221]
kick
Attacking a piece, often a knight, with a pawn, so that it will move. Kicking a piece may lead to gaining a tempo, or may force the opponent to concede control of key squares.[221]
The most important piece in chess. It may move to any adjacent square, and it may castle. A king threatened with capture is in check; a player cannot end their move with their king in check. If a player's king is in check and there is no escape, then the king is in checkmate, and the player loses. If the player whose turn it is has no legal moves and their king is not in check, then it is stalemate, and the game is drawn.
king bishop
Or king's bishop. The bishop that is on the kingside at the start of the game. Sometimes abbreviated "KB".[83]
A sustained attack on the enemy king that results in the king being driven a far distance from its initial position, typically resulting in its checkmate. Some of the most famous games featuring king hunts are Edward Lasker–Thomas, Polugaevsky–Nezhmetdinov, and Kasparov–Topalov.[222] Also called king chase.
king knight
Or king's knight. The knight that is on the kingside at the start of the game. Sometimes abbreviated "KN".[83]
king pawn
Or king's pawn. A pawn on the king's file, i.e. the e-file. Sometimes abbreviated "KP". Also king bishop pawn (KBP), king knight pawn (KNP), and king rook pawn (KRP) for a pawn on the f-, g-, or h-file, respectively.[83]
Or king's pawn opening. An opening that begins 1.e4.
king rook
Or king's rook. The rook that is on the kingside at the start of the game. Sometimes abbreviated "KR".[83]
kingside
Or king's side. The side of the board (half-board) the kings are on at the start of the game (the e- through h-file), as opposed to the queenside.[35] Also called king's wing.
king walk
A consecutive series of king moves designed to bring the king to a safer square. For example, if a player has castled kingside but the opponent has sacrificed a piece to destroy the kingside pawn cover, they may choose to walk the king over to the queenside to shelter behind the queenside pawns.[223] See also King walk.
A piece that may move to any nearest square not on a rank, file, or diagonal on which it stands. In other words, it may move two squares horizontally or vertically and then one square perpendicular to that (forming an L shape), jumping over any pieces in the way.
knight pawn
Or knight's pawn. A pawn on the knight's file, i.e. the b-file or g-file. Sometimes abbreviated "NP".[83]
A puzzle that challenges a person to set a knight on an empty chessboard, and make the piece move around (as it moves in a chess game), but to visit every square only once. The knight's tour is the best known of a variety of tours and puzzles based on chess pieces. A closed tour (also known as a re-entrant tour) ends on the same square on which it began and needs 64 moves. An open tour ends on a different square and needs only 63 moves.[224]
This phenomenon, described by Alexander Kotov in his 1971 book Think Like a Grandmaster, can occur when a player does not find a good plan after thinking long and hard on a position. The player, under time pressure, then suddenly decides to make a move that they have hardly thought about at all, and it may not be a good move for that reason.[225]
[from German, "war game"] Kriegspiel is a chess variant played by two opponents who can see only their own board, and one monitoring umpire who makes the moves of both players on a neutral board. It requires three chess sets and boards. The players make their moves based on limited information from the umpire. It was introduced in 1898. It is sometimes referred to as blind chess, not to be confused with blindfold chess.[226]
Kt
The symbol sometimes used for the knight when recording chess moves in descriptive notation, mainly in older literature. An N is used instead in algebraic notation and in later descriptive notation to avoid confusion with K, the symbol for the king.[22]
A well-known rook and pawn versus rook endgame position in which the player with the extra pawn can force a win by cutting off the opponent's king and placing a rook on the 4th rank in order to block the opponent's rook checks, thereby allowing the pawn to queen.[55]
The principal, most important, or most often played variation of an opening.[235]
majority
A larger number of pawns on one flank opposed by a smaller number of the opponent's; often a player with a majority on one flank has a minority on the other.[236] A central pawn majority is a larger number of pawns on the center files.
major piece
A queen or rook, also known as a heavy piece.[237] The primary distinction of major pieces versus minor pieces is that major pieces are capable of checkmate with only their own king for support, as the enemy king is unable to step across the ranks and files they control. On an otherwise empty board, a major piece can move from any square to any other square in at most two moves.
man
A piece or a pawn, when the term "piece" is used as exclusive of pawns.[238]
A bind on the light squares in the center, particularly d5, obtained by White by placing pawns on c4 and e4. Named for Géza Maróczy, it originally referred to formations arising in some variations of the Sicilian Defense, but the name is now also applied to similar setups in the English Opening and the Queen's Indian Defense. It was once greatly feared by Black but means of countering it have been developed since the 1980s and earlier.[239]
master
Loosely, a strong chess player who would be expected to beat most amateurs. It may also refer to a formal title such as International Master or National Master. Standards vary, but a master will usually have an Elo rating of over 2200.[240]
match
The term "match" does not refer to an individual game of chess, but to either a competition between two teams or a series of games between two individuals. A match may be the entire competition, or it may be a round in a knockout tournament or team tournament. A match between individuals usually consists of several games, continuing until one of the players has achieved either a set score or a set number of wins.[240]
A player's pieces and pawns on the board. The player with pieces and pawns of total greater value is said to have a material advantage. Gaining a material advantage is called winning material.[242] See Chess piece relative value.
materialism
Playstyle characterized by a willingness to win material at the expense of positional considerations. Chess engines historically were often materialistic.[243]
The part of a chess game that follows the opening and comes before the endgame, beginning after the pieces are developed in the opening. This is usually roughly moves 20 through 40.[242]
miniature
A short game (usually no more than 20 to 25 moves), for example: 1.e3 e5 2.Qf3 d5 3.Nc3 e4 4.Qf4?? Bd6! and White resigned in Spiel–Künzel, Europe 1900,[245] because the queen is trapped. However, some authors include games up to 30 moves.[246] Usually only decisive games (not draws) are considered miniatures. Ideally, a miniature should not be spoiled by an obvious blunder by the losing side. A miniature may also qualify as a brilliancy. The Opera Game is a famous example. Sometimes called a brevity [chiefly British].[52] See also Glossary of chess problems § miniature.
A smaller number of pawns on one flank opposed by a larger number of the opponent's; often a player with a minority on one flank has a majority on the other.[236]
An advance of pawns on the side of the board where one has fewer pawns than the opponent, an attack strategy usually carried out to provoke a weakness.[242]
minor piece
A bishop or knight.[242] Unlike major pieces, minor pieces are unable to contain the enemy king or block his advance alone, as he can simply pass through the holes in their line of attack. Compared to major pieces, minor pieces also find it difficult to navigate the entire board; a knight may require four moves to reach a square two squares away, while a bishop can only ever control half of all squares.
The ability of a piece(s) to move around the board. Having space.[242]
mouse slip
A fumble by a player in the use of a computer control tool while playing chess on the Internet that results in an unintended move.[249]
move
A full move is a turn by both players, White and Black. A turn by either White or Black is a half-move, or (in computer context) one ply.[250]
move order
The sequence of moves one chooses to play an opening or execute a plan. Different move orders often have different advantages and disadvantages. A plan that uses certain moves can sometimes be improved by making the identical moves but in a different sequence.[251] See also transposition.
mysterious rook move
Coined by Nimzowitsch to refer to the placing of a rook on a closed file in anticipation that the opponent is going to open the file. This move may either achieve a position with a rook on an open file, or it may alternatively hinder the opponent's intentions (prophylaxis). The meaning of the word has since expanded to refer to any rook move that appears to have a hidden purpose.[252][253]
An abbreviation sometimes used for the chess opening reference Nunn's Chess Openings. Cf. ECO and MCO.
NN
Traditionally used in game scores to indicate a player whose name is not known. The origin is uncertain. It may be an abbreviation of the Latin nomina ("names"), or it may be short for the Latin phrase nomen nescio ("name unknown").[254] Sometimes N.N.
A step toward earning a chess title, such as Grandmaster or International Master. To qualify for the award of norms, a tournament must be rated by FIDE, must be sufficiently strong, must include a mix of nationalities, must include a specified number of titled players, and must meet certain other requirements regarding time control and playing conditions. The score necessary to qualify for a norm depends on the strength of the tournament. In practice, three norms are usually required for a title, though regulations have varied over the years.[255][256]
Any method of recording chess moves, allowing games to be later published, replayed and analyzed. The most common notation today is algebraic notation, which is used internationally. Formerly descriptive notation was standard in English language publications. There are also systems of notation for recording chess positions without the use of diagrams, the most common of which is Forsyth–Edwards Notation (FEN).[257] Cf. annotation.
Occupation of a rank or file means a rook or queen controls it; occupation of a square means a piece or pawn sits on it.[258][259]
octopus
A strongly positioned knight in enemy territory. A knight not near the edge reaches out in eight directions, like the eight tentacles of an octopus.[260]
This refers to the stronger player giving the weaker player some sort of advantage in order to make the game more competitive. It may be an advantage in material, in extra moves, in time on the clock, or some combination of those elements. Since the advent of the chess clock, time odds have become more common than material odds.[261]
Any opening that begins with the moves 1.e4 e5. Examples of Open Games include the Ruy Lopez, the Giuoco Piano, the Danish Gambit, and many others. The Open Game is also referred to as a Double King's Pawn Opening or Double King's Pawn Game.
The beginning phase of the game, roughly the first dozen moves, but it can extend much farther. In the opening players set up their pawn structures, develop their pieces, and usually castle. The opening precedes the middlegame.[262]
Home study and analysis of openings and defenses that one expects to play, or meet, in later tournament or match games. In high-level play, an important part of this is the search for theoretical novelties that improve upon previous play or previously published analysis.[263]
opening repertoire
The set of openings played by a particular player. The breadth of different players' repertoires varies from very narrow to very broad.[264]
opening system
An opening that is defined by one player's moves and that can be played generally regardless of the moves of the opponent, with the goal of reaching a desired type of middlegame position. Sometimes several different move orders are possible. Examples include the Colle System and Hippopotamus Defense.[265]
A position in which two kings stand on the same rank, file, or diagonal with one empty square between them. The player to move may be forced to move the king to a less advantageous square. Opposition is a particularly important concept in endgames.[267] One orthogonal square separation is direct opposition; one diagonal square is diagonal opposition; multiple squares separation is distant opposition. Cf. corresponding squares.
optimal play
See Best response. Both sides playing their best move at each turn, or one of equally good alternatives. One side tries to win as quickly as possible while the other side tries to delay it as long as possible, or optimal play may result in a draw. Cf. Solved game § Perfect play.
An outpost is a square protected by a pawn that is in or near the enemy's stronghold. Outposts are a favorable position from which one can launch an attack, particularly using a knight.[269]
A passed pawn near the edge of the board and not in the path of threats from the opponent's pawns. In the endgame, such a pawn can constitute a strong advantage, because it threatens to promote, and it also diverts the opponent's forces to restrain its advance.[270]
overextended
An overextended position results when a player has advanced pawns too far into the opponent's side without sufficient support. The premature advance can leave weaknesses in the player's camp or the advanced pawns themselves may be weak ("overextended pawns").[271]
A piece that has too many defensive duties. An overloaded piece can sometimes be deflected, or required to abandon one of its defensive duties.[272]
overprotection
The strategy of protecting an important pawn or square more than is apparently necessary. This serves to dissuade the opponent from attacking that point, and the latent power of the "over protectors" assembled around an important point is a significant threat that can bear fruit at a small tactical change in the position. Aron Nimzowitsch coined the term and was a proponent of overprotection.[273]
over the board
1. An over-the-board game is played face to face with the opponent, as opposed to a remote opponent as in online chess or correspondence chess.
2. Analysis carried out during a game in real time (not necessarily a face-to-face game) as opposed to during preparation. Finding accurate moves over the board is harder than finding them with computer assistance in one's own time. "I looked up the gambit Smith played and there's a line that refutes it, but I couldn't find it over the board."[268]
Symbol used for the pawn when recording chess positions in English; a lowercase p is typically used for a Black pawn. Also used for the pawn when recording chess moves in descriptive notation, e.g. P-K4.
[from Italian, "to dodge the fight"] The former rule that a pawn could evade capture by an opposing pawn by its initial two-square advance, in contrast to the en passant rule. Passar battaglia remained the practice in several parts of Europe long after en passant was introduced, and it was not completely abandoned until 1880 when Italy adopted the en passant rule.[276]
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White with a passed pawn on b7. Black has a passed pawn on g6.
Describes a piece or pawn that is inactive and able to move to or control relatively few squares, or a position without possibilities for attack or counterplay.[273] Antonym: active.
passive sacrifice
The sacrifice of a piece, by moving a different piece, leaving the sacrificed piece under attack.
A part of chess thinking that involves remembering and recognizing certain recurring positional aspects large and small, visual and dynamic. It is a kind of thinking that gives an advantage to a player with great experience. It is distinct from the intellectual activity of calculation. It uses intuitive thinking that is familiar to humans, but is foreign to computers. It can be developed by studying chess puzzles. It has been studied by Adriaan de Groot, and other scientists, who have attempted to discover how chess players think.[278][279]
A piece that can move one square directly forward, or on its first move, can move two squares directly forward. It can also move one square diagonally forward when capturing. It may capture en passant. Upon reaching its eighth rank, it is promoted to a same-colored queen, rook, bishop, or knight.
A type of odds game, common in the 18th and 19th centuries, in which the superior player plays Black and begins the game with one of their pawns, usually the king bishop pawn, removed from the board; plus White gets an extra move at the start.[281]
pawn break
A pawn move that attacks an enemy pawn in order to open up lines and/or challenge the opponent's pawn structure. See also break.
Or pawn centre. A player's pawns in the center of the board. Pawns on the squares adjacent to the center may also be considered part of the pawn center. Having a strong pawn center was considered absolutely essential until the hypermodernist school introduced some new ideas.[282] Often shortened to center. See King's Indian Defense, Four Pawns Attack for an example of an opening leading to an extended pawn center.
pawn chain
Two or more pawns of the same color diagonally linked. A pawn chain's weakest point is the base because it is not protected by another pawn.[273] See also pawn structure.
Lichtenhein vs. Morphy, 1857
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Black has three pawn islands and White has two. The pawn on e5 is not isolated because it is adjacent to a file that has a white pawn.
pawn island
A group of pawns of one color on consecutive files with no other pawns of the same color on an adjacent file. A pawn island consisting of one pawn is an isolated pawn.[283]
The placement of the pawns during the course of a game. As pawns are the least mobile of the pieces and the only pieces unable to move backwards, the position of the pawns greatly influences the character of the game.[285] Also called pawn skeleton.
A number reflecting the approximate rating level at which a player performed in a particular tournament or match. It is often calculated by adding together the player's performances in each individual game, using the opponent's rating for a draw, adding 400 points to the opponent's rating for a win, and subtracting 400 points from the opponent's rating for a loss, then dividing by the total number of games. For example, a player who beat a 2400-rated player, lost to a 2600, drew a 2500, and beat a 2300, would have a performance rating of 2550 (i.e. 2800 + 2200 + 2500 + 2700, divided by 4).[286] Abbr. PR.
Often shortened to perpetual. When a player puts the opponent in check and the check could be repeated endlessly, the game will be declared a draw by repetition. This tactic can be resorted to as a form of insurance in a losing position.[287]
Usually refers to an important chess endgame that illustrates a drawing technique when the defender has a king and rook versus a king, rook, and pawn. It is also known as the third rank defense, because of the importance of the rook on the third rank cutting off the opposing king. It was analyzed by Philidor in 1777.[289] See also Rook and pawn versus rook endgame.
1. One of the chessmen or figures used to play the game – that is, a king, queen, rook, bishop, knight or pawn. Each piece type has its own rules of movement on the board and of capturing enemy pieces. This is the definition used in the context of rules of chess – for example, the touched piece rule.
2. When annotating or discussing chess games, the term "piece" usually excludes pawns. It may be used collectively for all "non-pawns" – for example, "White's pieces are well-posted." In some contexts, it may refer specifically to a minor piece – for example, "White is up two pieces for a rook."[291]
When a piece is attacked but cannot legally move, because doing so would expose the player's own king to the attack; or when a piece is attacked and can legally move out of the line of attack, but such a move would expose a more valuable piece (or an unprotected piece) to capture.[250] See absolute pin and relative pin, respectively.
playable
Said of an opening, a position, or move that gives the person playing it a tenable position.[292]
play by hand
To make a move intuitively and without analyzing the move.[293]
This is a popular computer-processible ASCII format for recording chess games (both the moves and related data).[288] There are import and export versions: the import version is lax, while the export version is not. Abbr. PGN.
position
"The disposition of pieces and pawns, of one or both colours, at any stage of the game or as set in a composition."[295] If one side has an overall advantage in strength, that side is said to have "the better position". If neither side has an overall advantage, the position might be called level or equal or balanced. The position of chessmen at the beginning of a game is called an array.[296]
positional play
Play based on strategy, on gaining and exploiting small advantages, and on analyzing the larger position, rather than calculating the more immediate tactics.[283] Cf. antipositional.
A sacrifice in which the lost material is not regained via a combination, but instead gains positional compensation. These typically require deep positional understanding and are often overlooked by computers[dubious – discuss]. Also known as a true sacrifice, as opposed to a pseudo sacrifice or sham sacrifice.[citation needed]
post mortem
Analysis of a game after it has concluded, typically by one or both players and sometimes with spectators (kibitzers) contributing as well. A player who has just lost the game thanks to a dubious move has the chance to "win the post-mortem" by finding a better one.[283]
In online chess, a move input that is made during the opponent's turn, to take effect only after the opponent has moved. Premoving, the act of making premoves, is a popular way of saving time in blitz and bullet formats.[297]
A well-analyzed novelty in the opening that is not published but first used against an opponent in competitive play.[298]
Principle of two weaknesses
A technique of increasing one's advantage by causing the opponent, who has one weakness, to have a second weakness. Even if both weaknesses are minor, the fact of having two, in practice, becomes a major weakness.[299]
Advancing a pawn to the eighth rank, converting it to a queen, rook, bishop, or knight. Promotion to a piece other than a queen is called underpromotion.[250]
A piece is protected when another friendly piece controls its square. This somewhat protects the first piece from capture, as there is the option to recapture. This is especially effective if the attacking piece is of greater value than than the threatened piece.
Or queen's knight. The knight that is on the queenside at the start of the game. Sometimes abbreviated "QN".[83]
queen pawn
Or queen's pawn. A pawn on the queen's file, i.e. the d-file. Sometimes abbreviated "QP". Also queen rook pawn (QRP), queen knight pawn (QNP), and queen bishop pawn (QBP) for a pawn on the a-, b-, or c-file, respectively.[83]
Or queen's pawn opening. An opening that begins 1.d4.
queen rook
Or queen's rook. The rook that is on the queenside at the start of the game. Sometimes abbreviated "QR".[83]
queenside
Or queen's side. The side of the board (board-half) the queens are on at the start of the game (the a- through d-file), as opposed to the kingside.[35] Also called queen's wing.
Symbol used for the rook when recording chess moves in English.[22]
Rabar Classification
A system of opening classification codes introduced by Braslav Rabar for Chess Informant. The system was used by Informant publications from 1966 to 1981 but has since been replaced by ECO codes.[308]
"A form of unorthodox chess designed to discount knowledge of the openings. The pawns are placed as in the array and behind them the pieces are placed in unorthodox fashion."[310] See also Fischerandom.
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White's ranks are indicated on the left (a-file); Black's relative reference to ranks are indicated on the right (h-file).
rank
A row of the chessboard. In algebraic notation, ranks are numbered 1–8 starting from White's side of the board; however, players customarily refer to ranks from their own perspectives. For example: White's king and other pieces start on their first (or "back" or "home") rank, whereas Black calls the same rank the "eighth" (or last) rank; White's seventh rank is Black's second; and so on. If neither perspective is given, White's view is assumed. This relative reference to ranks was formalized in the older descriptive notation.[311]
The capture of an opponent's piece that previously made a capture, and usually played immediately following the opponent's capture move. The capture and recapture occur on the same square, and usually the pieces captured and recaptured have the same value.
refute
To demonstrate that a strategy, move, or opening is not as good as previously thought (often, that it leads to a loss), or that previously published analysis is unsound. A refutation is sometimes colloquially referred to as a bust. A refutation in the context of chess problems or endgame studies is often called a cook.[313]
A pin where it is legal to move the pinned piece out of the line of attack. In other words, the piece is not pinned to the king, but to some other piece. Contrast with absolute pin where the pinned piece is not permitted to move, because the piece it is pinned to is the king.
remis
[from French] A draw. It literally means "reset" and is somewhat archaic (the usual word for a draw in modern French is nulle), but is internationally understood and may be used between players without a common language.
A reply is a response to an opponent's move. The most obvious example is that when your opponent puts your king in check, your reply is how you get it back out of check. When your opponent attacks one of your pieces, your reply might be moving it out of the way, protecting it, or interposing a less valuable piece between them. When your opponent captures one of your protected pieces, your reply might be retaliation.
A move a player has available. Such a move may not be crucial to the position on the board, but being able to force the opponent to move by making a reserve move can on occasion result in a significant advantage.[314]
To concede loss of the game. A resignation is usually indicated by stopping the clocks, sometimes by offering a handshake, or by saying "I resign". A traditional way to resign is by tipping over one's king. It is common for a game to be resigned, rather than for it to end with checkmate, because experienced players can foresee the checkmate.[315][316] However, under FIDE Laws, a player's resignation results in a draw if there is no sequence of legal moves that could lead to their opponent checkmating them.[317]
resign on time
A player who in a hopeless position intentionally runs out of time to avoid having to resign can be said to have resigned on time. This is usually performed in a more subtle manner than that of Curt von Bardeleben walking out of the tournament hall against Wilhelm Steinitz. A player low on time and in a losing position may simply "forget" to pay any attention to the clock.
A piece that may move along ranks and files without jumping.
rook lift
A maneuver that places a rook in front of its own pawns, often on the third or fourth rank. This can allow the rook to treat a half-open file as if it were an open file, or a closed file as if it were half-open.[319]
rook pawn
Or rook's pawn. A pawn on the rook's file, i.e. the a-file or h-file. Sometimes abbreviated "RP".[83]
This is a tournament in which each participant plays every other participant an equal number of times. In a double round-robin tournament the participants play each other exactly twice, once with white and once with black. A round robin tournament is commonly used if the number of participants is relatively small.[320] See also Swiss tournament.
A king or queen.[83] In chess variants, the term refers to any piece that must be protected from capture; under this definition, only the king is royal in orthodox chess.
A move or capture that voluntarily gives up material in return for an advantage such as space, development, or an attack. A sacrifice in the opening is called a gambit, especially when applied to a pawn.[315]
2. A player's score in a match or tournament, which is almost always 1 point for each win and ½ point for each draw. See Chess scoring.
score sheet
The sheet of paper used to record a game in progress. During formal games, it is usual for both players to record the game using a score sheet. A completed score sheet contains the game score.[190]
sealed move
To prevent unfair advantage when an OTB game is adjourned, the player whose turn it is to move is required to write down their next move and put it in a sealed envelope. Upon resumption, the arbiter opens the sealed envelope, makes the move and the game continues. The player may be disqualified if the sealed move is illegal, ambiguous or unclear. Adjournments and sealed moves are no longer standard practice. See also Adjournment (games).
second
An assistant hired to help a player in preparation for and during a major match or tournament. The second assists in areas such as opening preparation. The second also used to assist with adjournment analysis before the practice of adjournments was largely abandoned in the 1990s.[322]
second player
The expression "the second player" is sometimes used to refer to Black.
An opening that begins with White playing 1.d4 and Black replying with a move other than 1...d5.[323] Also called half-closed game.[324] See also Open Game and Closed Game.
An opening that begins with White playing 1.e4 and Black replying with a move other than 1...e5.[323] Also called half-open game.[324] See also Open Game and Closed Game.
The game is drawn if no capture or pawn move has occurred in the last seventy-five moves by either side, related to the fifty-move rule for looking at a series of moves without capture or pawn move.[325]
An offer of material that is made at no risk, as acceptance would lead to the gain of equal or greater material or checkmate. This is in contrast to a true sacrifice in which the compensation is less tangible. Also called pseudo sacrifice.[326]
sharp
Risky, double-edged, highly tactical. Sharp can be used to describe moves, maneuvers, positions, opening lines, and styles of play.[327]
Slang for an unexpected or sharp move that typically makes a tactical threat or technical challenge for the opponent.
silent move
A move that has a dynamic tactical effect on a position, but that does not capture or attack an enemy piece.[328][329] See also quiet move.
simplification
A strategy of exchanging pieces, often with one of the following goals: as a defensive measure to reduce the size of an attacking force; when having the advantage to reduce the opponent's counterplay; to try to obtain a draw; or as an attempt to gain an advantage by players who are strong in endgame play with simplified positions.[330] Also called liquidation.
An attack on a valuable piece, compelling it to move to avoid capture and thus expose a less valuable piece which can then be taken.[333][334] See also X-ray.
skittles
A casual or "pickup" game, usually played without a chess clock. At chess tournaments, a skittles room is where one goes to play for fun while waiting for the next formal game.[331]
slow
Describes a strategy that requires too many tempi to complete, allowing the opponent time to consolidate.
In the tournament played by Sofia rules, players are not allowed to draw by agreement. They could have draws by stalemate, threefold repetition, fifty-move rule, or insufficient material. Other draws are allowed only if the arbiter declares the game reached a drawn position.[336]
solid
An adjective used to describe a move, opening, or manner of play that is characterized by minimal risk-taking and emphasis on quietpositional play rather than wild tactics.
sortie
A queen development in front of its own pawns, often early in the opening, usually for the purpose of exploiting an advantage in space or punishing an error by the opponent. So called because the queen is usually developed behind its own pawns for its protection.
A tactic by which a queen, rook, or king progresses along a diagonal by making a series of lateral steps using a series of checks or alternating with pins and checks. Also called staircase movement.[339]
A position in which the player whose turn it is to move has no legal move and their king is not in check. A stalemate results in an immediate draw.[79]
The standard design of chess pieces, required for use in competition.[340]
stem game
A stem game is the chess game featuring the first use of a particular openingvariation. Sometimes, the player or the venue of the stem game is then used to refer to that opening.
strategic crush
Win characterized by gradual accumulation of advantages and complete prevention of counterplay.
The basis of a player's moves. The evaluation of positions and ways to achieve goals. Strategy is often contrasted with tactics, which are the calculations of more immediate plans and combinations.[341]
strong
An effective and well-placed piece or pawn; a potential outpost; a forceful or good move; a position having good winning chances; a highly rated player or one successful in tournaments; or a tournament having a sizable number of strong players competing, such as grandmasters. A "strong showing" refers to a player's high win ratio in a tournament. Antonym: weak, e.g. a weak square.
1. A "strongpoint defense" means an opening that defends and retains a central pawn (White: e4 or d4; Black: e5 or d5), as opposed to exchanging the pawn and relinquishing occupation of that central square.
2. More generically, a strongpoint can be any square heavily defended.
strong square
A square on a player's 4th or greater rank on which the player can post a piece that cannot or will not be driven away by enemy pawns.[343] Cf. weak square.
sudden death
The most straightforward time control for a chess game: each player has a fixed amount of time available to make all moves. See also fast chess.
support point
A square that cannot be attacked by a pawn, and that can be occupied as a home base for a piece, usually a knight.[341]
A system used in tournaments to determine pairings. In every round each player is paired with an opponent with the same or similar score.[344] See also round-robin tournament.
A symmetrical position on the chessboard means the positions of one's pieces are exactly mirrored by the opponent's pieces. This most often occurs when Black mimics White's opening moves. Black is said to break symmetry when making a move that no longer imitates White's move.[341]
[from Arabic: طبيعة ṭabīʕa, "essence"] Also tabiya. In chess openings a tabia is a key point. It may be a well-known "point of departure" where variations branch off, it may be a position that is reached so often that the real game begins after this initial series of book moves.[346][347]
Combinations, traps, and threats. Play characterized by short-term attacks, requiring calculation by the players, as distinguished from positional play.[341]
takeback
Used in casual games whereby both players agree to undo one or more moves.
tall pawn
[colloq.] An ineffective bishop, usually a bad bishop hemmed in by its own pawns.
The general principle that rooks usually should be placed behind passed pawns, either one's own or one's opponent's. Named after Siegbert Tarrasch.[348]
A unit of time considered as one move. A player may gain a tempo in the opening when the opponent moves the same piece twice. In the endgame, one may wish to lose a tempo by triangulation in order to gain the opposition.[341] Plural: tempos or tempi.
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This Scotch Opening position contains tension due to the knights on c6 and d4. Both knights are currently adequately defended, so neither player is forced to release the tension.
tension
A position in which one or more exchanges are possible, such as a pair of pawns facing each other on a diagonal where either can capture the other, is said to contain tension. Such a situation differs from a threat in that it does not need to be immediately resolved – for example, if both pawns are defended. The consequences of resolving the tension must be constantly considered by both players, in case there is a possibility of winning or losing material. This makes calculating the best move more complicated, and so there is a natural temptation to "release the tension" by making a like-for-like exchange (see simplification) or by moving the attacked piece. To "keep the tension" is to avoid resolving it, which can be good advice depending on the position.
text move
This term is used in written analysis of chess games to refer to a move actually played in the game as opposed to other possible moves. Often shortened to text, for example "The text is inferior as it allows...f5." Text moves are usually in bold whereas analysis moves are not.
thematic
Suited to the demands of the position. The term "thematic move" is often applied to the key move of a thematic plan.[349]
theme tournament
A chess tournament in which every game must begin with a particular opening specified by the organizers, for example the Budapest Gambit (1.d4 Nf6 2.c4 e5).
A draw may be claimed if the same position occurs three times with the same player to move; and with each player having the choice of the same set of moves each time, including the right to capture en passant and the right to castle.[352] For the same position occurring five times, see fivefold repetition.
1. The amount of time each player has to think and calculate as measured by a chess clock.
2. The number of moves to complete an objective; for example, if a king is racing to stop a pawn from queening, and the king has too few moves, that may be referred to as "not enough time".[341] See also tempo.
The allowed time to play a game, usually measured by a chess clock. A time control can require either a certain number of moves be made per time period (e.g. 40 moves in 2+1⁄2 hours) or it can limit the length of the entire game (e.g. five minutes per game for blitz). Hybrid schemes are used, and time delay controls have become popular since the widespread use of digital clocks.[86]
time delay
A time control that makes it possible for a player to avoid having an ever-decreasing amount of time remaining (as is the case with sudden death). The most important time delays in chess are Bronstein delay and Fischer delay.
time pressure
Or time trouble. Having very little time on one's clock (especially less than five minutes) to complete one's remaining moves. Also called zeitnot. See also time control.
Or touched piece rule. The rule that requires a player who touches a piece to move that piece unless the piece has no legal moves. If a player moves a piece to a particular square and takes their hand off it, the move must be to that square if it is a legal move. Castling must be initiated by moving the king first, so a player who touches their rook may be required to move the rook, without castling. The rule also requires a player who touches an opponent's piece to capture it if possible. In order to adjust the position of a piece within its square without being required to move it, the player should say "J'adoube" or "I adjust".[351]
A competition involving more than two players or teams, generally played at a single venue (or series of venues) in a relatively short period of time. A tournament is divided into rounds, with each round consisting either of individual games or matches in the case of knockout tournaments and team tournaments. The assignment of opponents is called pairing, with the most popular systems being round-robin and Swiss. A tournament is usually referred to by the city in which it was played and the year, such as "London 1851", although there are well-known exceptions, such as "AVRO 1938".
tournament book
A book recording the scores of all the games in a tournament, usually with analysis of the best or most important games and some background on the event and its participants. One well-known example is Bronstein'sZurich International Chess Tournament 1953. The less comprehensive tournament bulletin is usually issued between the rounds of a prestigious event, giving the players and world media an instant record of the games of the previous round. Individual copies may be bundled together at the conclusion of the event to provide an inexpensive alternative to the tournament book.[353]
tournament director
Organizer and arbiter of a tournament, responsible for enforcing the tournament rules and the laws of chess. Abbr. TD. Also tournament controller [chiefly British].
Also Troitzky line. Endgame analysis by Alexey Troitsky of two knights versus a pawn found certain pawn positions that result in win, draw or loss. The resulting pawn positions on each file form what is known as the Troitsky line or Troitsky position.[358]
A tactic (also known as "removal of the guard") in which a defensive piece is captured, leaving one of the opponent's pieces undefended or underdefended.[361]
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White to move should underpromote the c7-pawn to a rook; promoting to a queen gives stalemate.
Promoting a pawn to a rook, bishop, or knight instead of a queen. Rarely seen unless the knight can deliver a crucial check, or when promotion to a rook or a bishop instead of a queen is necessary to avoid stalemate.[250]
1. A sequence of moves or an alternative line of play, often applied to the opening. A variation does not have to have been played in a game; it may also be a possibility that occurs only in analysis.[354] Also called continuation.
2. The word "Variation" is also used to name specific sequences of moves within an opening. For an example, the Dragon Variation is part of the Sicilian Defense.[84]
A move whose sole purpose is to oblige the opponent to move. A waiting move is effective when the opponent has nothing but bad moves available (i.e. is in zugzwang).[363]
A pawn or square that can be attacked and is hard to defend.[365]
weak square
A square that cannot be easily defended from attack by an opponent. Often a weak square is unable to be defended by pawns (a hole) and can be theoretically occupied by a piece. Exchange or loss of a bishop may make all squares of that bishop's color weak resulting in a "weak square complex" on the light squares or the dark squares.[366]
The light-colored squares on the chessboard are often referred to as "the white squares" even though they often are some other light color. Similarly, "the white pieces" are sometimes actually some other (usually light) color.[37] See also black.
The designation for the player who moves first, even though the corresponding pieces, referred to as "the white pieces", are sometimes actually some other (usually light) color. See also Black and first-move advantage.
A combination in which two pieces work together to deliver an alternating series of checks and discovered checks in such a way that the opposing king is required to move on each turn. It is a potent technique, since, on every other move, the discovered check may allow the non-checking piece to capture an enemy piece without losing a tempo. The most famous example is Torre–Lasker, Moscow 1925.[370] Also called seesaw.
wing
The queenside a-, b-, and c-files; or the kingside f-, g-, and h-files.[371] Also called flank.
The name given to variations of several openings in which one player gambits a wing pawn, usually the b-pawn.[372]
winning percentage
A number calculated by adding together the number of games won and half of the number of games drawn (i.e. ignoring the losses), then dividing that total by the total number of games that were played.
Another way of calculating the winning percentage is by taking the percentage of games won by a player plus half the percentage of drawn games. Thus, if out of 100 games a player wins 40 percent, draws 32 percent, and loses 28 percent, the winning percentage is 40 plus half of 32, i.e. 56 percent.[373]
winning position
A position is said to be a winning one if one specified side, with correct play, can eventually force a checkmate against any defense (i.e. perfect defense).[374] Also called won game.
Or wrong-colored bishop. A bishop that, because of the color squares it is restricted to, suffers critical loss of utility in the game position. See also wrong rook pawn.[376]
When the power of a piece, either to attack or to defend, seems to pass through an intervening enemy piece. An X-ray attack, also known as a skewer, occurs when two pieces of the same color are caught in the same line of attack along a diagonal, rank, or file. The attacking piece forces the first and more valuable piece to move out of the way, which allows the second piece to be captured. An X-ray defense occurs when one piece is defended by another piece through an attacking enemy piece standing between the two.[378]
[from German, "time need"] Having very little time on the clock to complete the remaining moves of a timed game.[379] Also called time pressure and time trouble. See also time control.
[from German, "compulsion to move"] When a player is put at a disadvantage by having to make a move; where any legal move weakens the position. Zugzwang usually occurs in the endgame, and rarely in the middlegame.[381]
zwischenschach
[from German, "in-between check"] Playing a surprising check that the opponent did not consider when plotting a sequence of moves; a zwischenzug that is a check.[382]
[from German, "in-between move"] An "in-between" move, or an intermezzo, played before an expected reply. Often, but not always, this involves responding to a threat by posing an even greater threat, forcing the opponent to respond to the threat first.[383]
^Staunton, Howard (1876). Chess: Theory and Practice. pp. 48–49. When the King is directly attacked by an adverse man, the move is called simply check; when the Piece or Pawn moved does not itself attack the King, but unmasks another which does, it is called a discovered check; and when both the man moved and the one unmasked attack the King, they are said to give double check.
^Reinfeld, Fred (1955). 1001 Winning Chess Sacrifices and Combinations. p. 74. ISBN0-87980-111-5. Discovered check is really a kind of discovered attack, with this important difference: the "discovering" piece moves away to allow its colleague to give check along the vacated line.
^Golombek 1977, p. 113, and Silman 1999, p. 432, define an exchange to always be of equal value, but most writers do not: Horton 1952, p. 63; Brace 1977, p. 97; Hooper & Whyld 1996, p. 130; Seirawan & Silman 1994, p. 188.
^[2] Klein, Mike. "Five Crowned In ChessKid.com National Championship". The United States Chess Federation website.9 June 2015 "The rules specify that mouse-slips stand, so Perkins' win drew him even with Vaidya at 3.0/4."
^Reinfeld, Fred (1955). 1001 Winning Chess Sacrifices and Combinations. p. 151. ISBN0-87980-111-5. The X-ray attack, or skewer attack, is the opposite of the pin. In the X-ray attack, a piece attacks a hostile piece which is situated on a line with another piece of lesser value. When the attacked piece moves off the line, it exposes the second piece to capture.
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