Terms

Active - Describes a piece that is able to move or control many squares

Advanced pawn - A pawn that is on the opponent's side of the board (the fifth rank or higher). 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 his mobility. An advanced passed pawn that threatens to promote can be especially strong.

Artificial castling - Refers to a maneuver of several single moves by the king and a rook where they end up as if they had castled.

Backward pawn - A pawn that is behind the pawns of the same color on the adjacent files and that cannot be advanced with the support of another pawn.

Bad bishop - A bishop which is hemmed in by the player's own pawns.

Battery - 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 will be delivered. The term is also used in cases where moving the middle piece will uncover a threat along the opened line other than a check.

Bishop pair - In open positions, two bishops (on opposite colors) are considered to have an advantage over two knights or a knight and a bishop. (In closed positions knights may be more valuable than bishops.) The player with two bishops is said to have the bishop pair.

Blockade - A strategic placement of a minor piece directly in front of an enemy pawn, where it restrains the pawn's advance and gains shelter from attack. Blockading pieces are often overprotected.

Break - A pawn advance or capture that opens up a blocked position.

Castling - A special move involving both the king and one rook. Its purpose is generally to protect the king and develop the rook. Castling on the kingside is sometimes called castling short and castling on the queenside is called castling long; the difference is based on whether the rook moves a short distance (two squares) or a long distance (three squares).

Centralization - Moving a piece or pieces toward the center of the board. In general, pieces are best placed in or near the center of the board because they control a large number of squares and are available for play on either flank as needed. Because of their limited mobility, knights in particular benefit from being centralized. There are several chess aphorisms referring to this principle: "A knight on the rim is dim" (or "grim" instead of "dim") and "A knight on the side cannot abide."

Central pawn - A pawn on the king's file or queen's file, i.e. on the d-file or e-file.

Closed file - A file on which black and white both have a pawn.

Combination - A clever sequence of moves, often involving a sacrifice, to gain the advantage. The moves of the other player are usually forced, i.e. a combination does not give the opponent too many possible lines of continuation.

Connected pawns - Refers to two or more pawns of the same color on adjacent files. See also isolated pawns.

Connected passed pawns - 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. Also see connected pawns.

Connected rooks - 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. cf.Doubled rooks.

Counterplay - Active maneuvering by the player in an inferior or defensive position.

Cramped - A position with limited mobility.

Deflect - To cause a piece to move to a less suitable square. Typically used in the context of a combination or attack, where the deflected piece is critical to the defence.

Double attack - 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 (a situation which may arise via a discovered attack in which the moved piece also makes a threat). The attacks may directly threaten opposing pieces, or may be threats of another kind: for instance, to capture the queen and deliver checkmate.

Double check - A check delivered by two pieces at the same time. A double check necessarily involves a discovered check.

Doubled pawns - A pair of pawns of the same color on the same file

Doubled rooks - Two of a player's rooks placed on the same file or rank.

En passant - ("in the act of passing"; derived from French) The rule that allows a pawn that has just advanced two squares to be captured by a pawn on the same rank and adjacent file. The pawn is therefore taken as if it had only moved one space. It is only possible to take en passant on the next move.

Endgame - The stage of the game when there are few pieces left on the board. The endgame follows the middlegame.

Escape square - A square to which a piece can move, which allows it to escape attack. See also flight square and luft.

Exchange - The capture of a pair of pieces, one white and the other black, usually of the same type (i.e rook for rook, knight for knight etc). - The exchange is used to refer to the advantage of a rook over a minor piece (knight or bishop). The player who captures a rook while losing a minor piece is said to have won the exchange, and the opponent is said to have lost the exchange. An exchange sacrifice is giving up a rook for a minor piece.

Fianchetto - Refers to a bishop developed to the second square on the file of the adjacent knight (that is, b2 or g2 for white, b7 or g7 for black), or the process of developing a bishop to such a square. It usually occurs after moving the pawn on that file ahead one square (or perhaps two). The Italian word is actually a noun ("in fianchetto") and not a verb.

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, the f-file or the king bishop file comprises the squares f1–f8 or KB1–KB8.

Flank - The queenside a, b, and c-files, or the kingside f, g, and h-files, also called wing; distinguished from the center d and e-files.

Forced move - A move which is the only one which does not result in a serious disadvantage for the moving player.

Gambit - A sacrifice (usually of a pawn) used to gain an early advantage of space and /or time in the opening.

Good bishop - A bishop which has high mobility, typically because the player's pawns are on squares of color opposite to that of the bishop. (See #Bad bishop.)

Half-open file - A file on which only one player has no pawns.

Hanging - Unprotected and exposed to capture. Slang for en prise. To "hang a piece" is to lose it by failing to move or protect it.

Initiative - The advantage that a player who is making threats has over the player who must respond to them. The attacking player is said to "have the initiative". s/he can often turn the play as s/he wills. The initiative often results from an advantage in time and/or space.

Isolated pawn - A pawn with no pawn of the same color on an adjacent file.

King hunt - 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.

Kingside - The side of the board where the kings are at the start of the game (the e through h files), as opposed to the queenside.

Long diagonal - One of the two diagonals with eight squares (a1-h8 or h1-a8).

Majority - A larger numbers 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.

Mating attack - An attack aimed at checkmating the enemy king.

Middlegame - 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.

Open file - A file on which there are no pawns. A file on which only one player has no pawns is said to be half-open.

Open game - A game in which exchanges have opened files and diagonals, as opposed to a closed game.

Opening - The beginning moves of the game, roughly the first 10-20 moves. In the opening players set up their pawn structures, develop their pieces, and typically castle. The opening precedes the middlegame.

Opposition - A situation 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.

Outpost - An outpost is a square protected by a pawn that is in or near the enemy's stronghold. Outposts are a favourable position from which to launch an attack, particularly using a knight.

Overextended - A position where a player has moved a piece or group of pieces (usually pawns) away from the rest in such a way that they are too difficult to defend.

Overprotection - The technique of massing forces in support of a strong point, often a Blockade.

Overworked/Overloaded - A piece that has too many defensive duties. An overloaded piece can sometimes be deflected, or required to abandon one of its defensive duties.

Passive - A piece that is able to move to or control relatively few squares, also referred to as an inactive piece. See active.

Passed pawn - A pawn that has no pawn of the opposite color on its file or on any adjacent files on its way to queening.

Patzer - A weak chess player, also referred to as a "fish", "woodpusher" or "duffer". (German: patzen, to bungle.)

Pawn chain -A locked diagonal formation of pawns, each one supported by a friendly pawn diagonally behind and blocked by an enemy pawn directly ahead.

Pawn island - A group of pawns of one color on consecutive files with no other pawns of the same color on any adjacent files. A pawn island consisting of one pawn is called an isolated pawn.

Pawn storm - An attacking technique where a group of pawns on one wing is advanced in order to break up the defense.

Pawn structure - The placement of the pawns is known as the pawn structure. 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.

Perpetual check - A draw forced by one player putting the opponent's king in a potentially endless series of checks.

Positional play - Play dominated more by long-term maneuvering for advantage than by short-term attacks and threats, and requiring judgment more than extensive calculation of variations, as distinguished from tactics.

Promotion - 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.

Prophylaxis (adjectival form: prophylactic) - a move that frustrates an opponent's plan or tactic; - a strategy in which a player frustrates tactics initiated by the opponent until a mistake is made. - Prophylactic techniques include the blockade, overprotection, and the mysterious rook move.

Protected passed pawn - A passed pawn that is supported by another pawn.

Push - To move a pawn forward.

Quiet Move - A move which does not attack or capture an enemy piece.

Rank - A row of the chessboard. Specific ranks are referred to by number, first rank, second rank, …, eighth rank. Unlike the case with files, rank names are always given from the point of view of each individual player, with the first rank being the home row of the king and other pieces. White's first rank is Black's eighth rank and White's eighth is Black's first, White's second rank is Black's seventh rank and White's seventh is Black's second, and so on.

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.

Royal fork - A fork between king and queen.

Sac - Short for sacrifice, usually used to describe a sacrifice for a mating attack.

Sacrifice - When one player 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.

Simplification - A strategy of exchanging pieces of equal value. Simplification can be used defensively to reduce the size of an attacking force. It can also be used by a player with an advantage in order to amplify that advantage or reduce the opponent's counterplay. Simplification is also used as an attempt to obtain a draw, or as an attempt to gain an advantage by players who are strong in endgame play with simplified positions.

Space - The squares controlled by a player. A player controlling more squares than the other is said to have a spatial advantage.

Spite check - A harmless check given by a player who is about to be checkmated that serves no purpose other than to momentarily delay the defeat.

Stalemate - A position in which the player whose turn it is to move has no legal move and his king is not in check. A stalemate results in an immediate draw.

Tactics - Play characterized by short-term attacks and threats, often requiring extensive calculation by the players, as distinguished from positional play.

Tempo - An extra move, an initiative at development. A player gains a tempo (usually in the opening) by making the opponent move the same piece twice or defend an enemy piece. In the endgame, one may wish to lose a tempo by triangulation to gain against the opposition. (Plural: tempos or tempi).

Threefold repetition - A draw may be claimed if the same position occurs three times with the same player to move, and with each player having the same set of legal moves each time (the latter includes the right to take en passant and the right to castle).

Triangulation - A technique used in king and pawn endgames (less commonly seen with other pieces) to lose a tempo and gain the opposition.

Waiting move - A passive but harmless move, which is played while waiting for initiative from the opponent.

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.

Windmill - 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.

X-ray - "Seeing through" another piece at the piece behind it.

Zugzwang - (from the German) 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.