Chess glossary — 200 terms explained
Clear, illustrated definitions of every chess term, from tactics to endgames.
- Endgame
Active king
An active king is a king that participates directly in the game by moving toward the center or the opponent’s pawns to exert concrete pressure on the position.
- Strategy
Active piece
An active piece in chess is a piece placed on a square where it controls as many squares as possible, participates in threats, and contributes fully to the game — whether attacking or defending.
- Rules
Algebraic notation
Algebraic notation is the universal writing system used in chess to record moves by identifying each square with a letter (file) and a number (rank).
- Tactics
Arabian mate
The Arabian mate is a checkmate pattern in which a rook and a knight combine to deliver mate against a king trapped in a corner: the rook delivers the final check while the knight defends it and seals the last escape square.
- Tactics
Attraction
Attraction in chess is a tactical motif that forces an opponent’s piece — most often the king or a major piece — to move to a disadvantageous square, where it becomes vulnerable to a decisive combination.
- Tactics
Back rank mate
The back rank mate is a checkmate that occurs when a king is trapped on its back rank (the first or eighth rank) and is checkmated by an enemy rook or queen sliding onto that row.
- Pawn structure
Backward pawn
A backward pawn is a pawn that can no longer be supported by a friendly pawn and stands on a half open file, making it a structural weakness that is difficult to defend.
- Strategy
Bad bishop
A bad bishop is a bishop whose mobility is severely restricted because its own pawns are fixed on squares of the same color, trapping it behind its own pawn structure.
- Tactics
Battery
A battery in chess is a setup in which two pieces of the same color are aligned on the same line — a file, rank, or diagonal — so that the rear piece reinforces and amplifies the power of the front piece.
- Material
Bishop
The bishop is a chess piece that moves diagonally any number of squares, always remaining on the same color square throughout the game.
- Endgame
Bishop endgame
A bishop endgame is a phase of the game in which both sides have only bishops (and possibly pawns) remaining on the board.
- Strategy
Bishop pair
The bishop pair refers to owning both bishops — the light squared and the dark squared — while the opponent has lost one or both of theirs.
- Rules
Blitz
Blitz chess is a fast paced format in which each player is given a very short amount of time for the entire game — typically between 3 and 5 minutes per player, with or without an increment (extra seconds added after each move).
- Strategy
Blockade
A blockade is a strategic technique that consists of placing a piece directly in front of an opponent’s pawn in order to immobilize it and halt its advance.
- Tactics
Boden’s mate
Boden’s mate is a checkmate pattern delivered by two bishops whose diagonals intersect to trap the enemy king in a crossfire, typically following a sacrifice that opens the necessary lines.
- Opening
Book move
A book move is a move recorded in opening theory, considered correct or optimal based on decades of analysis by players and chess engines.
- Rules
Bullet
Bullet chess is a time control format in which each player has a very short total time — typically one minute (1+0) or slightly more with a small increment (such as 1+1 or 2+1) — to make all their moves throughout the game.
- Strategy
Candidate move
A candidate move is any move a player identifies as worth analyzing before making a final decision.
- Pawn structure
Candidate pawn
A candidate pawn is a pawn that has the potential to become a passed pawn once the opposing pawns on adjacent files are exchanged or eliminated.
- Opening
Castling
Castling is a special chess move that allows the king to find safety while activating a rook, all in a single turn.
- General
Center
The center in chess refers to the four central squares of the board — e4, d4, e5, and d5 — as well as the surrounding squares that form what is known as the extended center (c3, c4, c5, c6, d3, d6, e3, e6, f3, f4, f5, f6).
- Strategy
Center control
Center control refers to the strategic command of the central squares of the chessboard — primarily e4, d4, e5, and d5 — through pawns, pieces, or a combination of both.
- Pawn structure
Central pawn
A central pawn is a pawn placed on one of the four central squares of the board (e4, d4, e5, d5) or, more broadly, on the c, d, e, or f files.
- Strategy
Centralization
Centralization in chess refers to the strategic principle of placing pieces on or near the center of the board — squares e4, d4, e5, d5 and their neighbors — in order to maximize their range and overall influence on the game.
- Rules
Check
In chess, check is a situation in which a player’s king is directly attacked by one or more of the opponent’s pieces.
- Rules
Checkmate
Checkmate is the decisive final position in a chess game, in which a player’s king is in check (attacked by one or more opposing pieces) and has no legal way to escape: it cannot move to a safe square, block the attack with another piece, or capture the attacking piece.
- Rules
Chess clock
A chess clock is a timing device that assigns a separate, limited amount of thinking time to each player, counting down each one’s time alternately to ensure games are completed within a defined time frame.
- General
Chessboard
The chessboard is the playing surface on which a chess game takes place: it consists of 64 squares arranged in an 8×8 grid, with alternating light and dark squares.
- Rules
Classical
Classical time control in chess refers to a format where each player has a long thinking time — typically 90 minutes or more for the entire game, often supplemented by an increment added after each move.
- Opening
Closed center
A closed center is a pawn structure in which the central pawns of both sides are locked against each other, forming an interlocking chain that prevents any open files from emerging in the middle of the board.
- Pawn structure
Closed structure
A closed structure is a pawn configuration where both sides' pawns are interlocked, mutually blocking each other and sealing the central files.
- Tactics
Combination
A combination in chess is a forced sequence of moves, often involving a sacrifice, that leads to a clearly favorable outcome — material gain, checkmate, or a decisive advantage — against the opponent’s best defense.
- Strategy
Compensation
Compensation in chess refers to the set of non material advantages — initiative, piece activity, centre control, pawn structure — that offset a deficit in material or another type of imbalance.
- Material
Compensation for material
Material compensation refers to the situation where a player deliberately gives up material — pieces or pawns — in exchange for concrete advantages of a different nature, such as the initiative, piece activity, a favourable pawn structure, or a promising attack.
- Pawn structure
Connected pawns
Connected pawns are two or more pawns of the same color placed on adjacent files, able to support each other as they advance.
- Strategy
Converting an advantage
Converting an advantage in chess means transforming an existing edge — whether material, positional, or dynamic — into a concrete result: a win by checkmate or by the opponent’s resignation.
- Opening
Counter-gambit
A counter gambit is an opening in which a player responds to the opponent’s offer by sacrificing a pawn of their own, rather than simply accepting or declining.
- Tactics
Counterattack
A counterattack in chess is a response to an opponent’s threat that, rather than defending passively, creates an equal or greater threat in return, forcing the opponent to react.
- Tactics
Damiano’s mate
Damiano’s mate is a checkmate pattern in which a queen drives the enemy king to the edge of the board through a series of checks, before delivering mate with the support of a pawn that seals off the king’s last escape square.
- Opening
Defense
A defense in chess is an opening system chosen by the second player (Black) to respond to White’s initial moves and challenge their natural first move advantage.
- Tactics
Deflection
Deflection is a tactical motif that forces an opponent’s piece away from a square or line it is protecting, compelling it to move somewhere less useful — typically through a capture or an immediate threat.
- Opening
Development
Development in chess refers to the process of moving pieces from their starting squares to active positions where they can influence the game.
- General
Diagonal
A diagonal in chess is a line of same colored squares running at an angle across the board, along which bishops and queens move.
- Endgame
Direct opposition
Direct opposition is an endgame configuration in which the two kings face each other on the same rank or file, separated by exactly one square, with the opponent having the move.
- Tactics
Discovered attack
A discovered attack is a tactical move in which one piece moves away and, in doing so, uncovers an attack by an allied piece that was sitting behind it on the same rank, file, or diagonal.
- Tactics
Discovered check
A discovered check is a tactical device in chess where moving one piece reveals an attack on the opponent’s king by another piece that was previously blocked behind it on the same rank, file, or diagonal.
- Endgame
Distant opposition
Distant opposition is an endgame technique in which the two kings face each other on the same file or rank, separated by an odd number of squares greater than one — typically three or five — so that the side not to move holds the opposition.
- Strategy
Domination
Domination in chess refers to a situation where an opponent’s piece is unable to move freely — or is effectively trapped — without being formally pinned or directly captured: it is simply confined to a zone fully controlled by your pieces.
- Tactics
Double attack
A double attack is a tactic that threatens two of the opponent’s targets simultaneously with a single move, forcing them to choose which one to save.
- Tactics
Double check
A double check is a situation in which the opponent’s king is attacked by two pieces simultaneously in a single move — a special case of a discovered check where the moving piece itself also gives check.
- Pawn structure
Doubled pawn
Doubled pawns are two pawns of the same colour placed on the same file after a capture has occurred.
- Rules
Draw
A draw in chess is a result in which neither player wins: the game ends in a tie, and both players score 0.5 points in tournament play.
- Rules
Draw by agreement
A draw by agreement is a way to end a chess game in which both players mutually decide to share the point, with neither side claiming victory.
- Rules
Draw by repetition
A draw by repetition is a chess rule that allows a player to claim a draw when the same position — including the same side to move, the same castling rights, and the same en passant possibilities — occurs three times during the game.
- Strategy
Dynamic play
Dynamic play in chess refers to a style of play centered on piece activity, initiative, and the creation of concrete threats, rather than the patient accumulation of long term structural advantages.
- Rules
ELO rating
The ELO rating is a mathematical system that assigns each chess player a number reflecting their playing strength, making it possible to compare players and find balanced opponents.
- Rules
En passant
En passant is a special chess rule that allows a pawn to capture an adjacent enemy pawn that has just advanced two squares from its starting position, as if it had only moved one square.
- Endgame
Endgame zugzwang
Endgame zugzwang is a situation in which the player whose turn it is to move is forced to worsen their own position, because every legal move available to them is detrimental.
- Tactics
Epaulette mate
The epaulette mate is a checkmate pattern in which the enemy king is mated on a rank or file while two of its own pieces block both lateral escape squares — resembling the epaulettes on a military uniform flanking it on either side.
- Tactics
Exchange sacrifice
The exchange sacrifice is a tactical or strategic decision in which a player voluntarily gives up a rook for a bishop or knight — that is, surrenders "the exchange" (the value gap between a rook and a minor piece) — in return for concrete compensation such as an attack, an improved pawn structure,…
- Tactics
Favorable exchange
A favorable exchange in chess is a tactical or strategic operation in which a player captures an opponent’s piece of greater value than the one given up in return, thereby gaining a net material advantage.
- General
FEN
FEN (Forsyth Edwards Notation) is a standardized text format that describes a complete chess position in a single line of text.
- Opening
Fianchetto
A fianchetto is the development of a bishop to b2 or g2 (for White) or b7 or g7 (for Black), preceded by advancing the pawn to b3/g3 (or b6/g6), placing the bishop on the long diagonal to control the center from the flank.
- Rules
FIDE
FIDE (Fédération Internationale des Échecs — the International Chess Federation) is the world governing body for competitive chess, responsible for setting the official rules of the game and managing international ratings, including the widely used ELO rating system.
- Endgame
Fifty-move rule
The fifty move rule is an official chess rule that allows a player to claim a draw if fifty consecutive moves have been played by each side without any pawn move or capture.
- General
File
A file is a vertical line on the chessboard, connecting all squares that share the same letter from rank 1 to rank 8.
- Opening
First-move advantage
The first move advantage refers to the structural edge that White enjoys by moving first in a game of chess.
- General
Flank
In chess, the flank refers to either of the two lateral halves of the board: the kingside (files e through h) or the queenside (files a through d).
- Tactics
Forced defense
A forced defense is a tactical situation in which a player has only one legal or reasonable reply to an opponent’s threat, under penalty of suffering a decisive material loss or immediate checkmate.
- Tactics
Fork
A fork is a chess tactic in which a single piece attacks two or more enemy pieces at the same time, forcing the opponent to give up at least one of them.
- Strategy
Fortress
A fortress is a defensive technique in which the materially inferior side builds an impregnable position, forcing the opponent to accept a draw because they cannot break through.
- Opening
Gambit
A gambit is an opening in which a player voluntarily sacrifices a pawn — or sometimes a piece — in the very first moves of the game, in exchange for compensation such as a lead in development, central control, or initiative.
- Strategy
Good bishop
A good bishop is a bishop whose diagonals are not obstructed by its own pawns, allowing it to move freely and exert maximum influence across the board.
- Tactics
Greco’s mate
Greco’s mate is a checkmate pattern in which a rook (or queen) delivers check to the enemy king along the file it occupies, while a bishop controls the diagonal escape square, making any flight impossible.
- Pawn structure
Hanging pawns
Hanging pawns are a pair of adjacent allied pawns on the same rank, with no supporting pawns on the neighboring files, unable to defend each other against a direct frontal attack.
- Pawn structure
Hole
A hole in chess is a square in your own camp that no friendly pawn can ever control, allowing an enemy piece to settle there permanently without risk of being chased away by a pawn.
- Rules
Increment
In chess, an increment is an amount of time automatically added to a player’s clock after each move, preventing games from ending purely on time pressure.
- Strategy
Initiative
In chess, the initiative refers to a player’s ability to set the pace of the game by creating threats that force the opponent to react, rather than pursue their own plans.
- Endgame
Insufficient material
Insufficient material is a situation in which a player no longer has the pieces needed to deliver checkmate, regardless of how the position plays out.
- Tactics
Interference
Interference in chess is a tactical motif that involves placing a piece on the line shared by two enemy pieces of the same color, severing their mutual coordination and exposing the weakness that results.
- Pawn structure
Isolated pawn
An isolated pawn is a pawn that has no friendly pawns on either adjacent file, meaning it can only be defended by pieces, never by another pawn.
- Endgame
Key squares
Key squares are specific squares on the board whose lasting occupation by the king (or another piece) guarantees the conversion of an endgame advantage, most commonly by ensuring a pawn's promotion.
- Material
King
The king is the most important piece in chess: the game is lost the moment your king is checkmated — attacked with no way to escape.
- Endgame
King and pawn vs king
The king and pawn vs king endgame is one of the most fundamental endings in chess: one side has a king and a single pawn against a lone king.
- Endgame
King and queen mate
The king and queen mate is a fundamental chess endgame technique that consists of forcing the opposing king to the edge or corner of the board using your king and queen, then delivering checkmate.
- Endgame
King and rook mate
King and rook mate is a fundamental endgame technique in which the stronger side uses a king and a rook to force the opponent’s king to the edge of the board and deliver checkmate.
- Endgame
King centralization
King centralization is the endgame principle of bringing the king toward the center of the board so that it becomes an active piece.
- Pawn structure
King pawn
The king pawn is the pawn standing in front of the king at the start of the game — the pawn on the e file (e2 for White, e7 for Black).
- General
Kingside
The kingside refers to the right half of the chessboard from White’s perspective — the f, g, and h files (and often the e file depending on context) — the side where the white king starts the game and where the short castle (O O) shelters it behind a pawn barrier.
- Opening
Kingside castling
Kingside castling is a special move in which the king shifts two squares toward the kingside and the nearest rook moves to the other side of the king, all in a single action.
- Material
Knight
The knight is one of the six chess pieces, instantly recognizable by its horse head shape and its distinctive L shaped move: two squares in one orthogonal direction, then one square perpendicular to that, or vice versa.
- Endgame
Knight endgame
A knight endgame is a phase of the game in which both sides have only knights (and pawns) remaining as active pieces, with no rooks, bishops, or queens on the board.
- Tactics
Ladder mate
The ladder mate is an endgame checkmate pattern in which two rooks (or a rook and a queen) progressively drive the opposing king to the edge of the board by stripping away one rank or file at a time, until checkmate is delivered.
- Opening
Leaving theory
Leaving theory refers to the moment in a chess game when one of the players departs from the established and studied opening moves, stepping into uncharted territory where both players must start thinking for themselves.
- Tactics
Legal’s mate
Legal’s mate is a tactical combination in which a player sacrifices their queen to deliver checkmate using minor pieces — typically two knights and a bishop — by breaking a relative pin on the knight on f3.
- Endgame
Lucena position
The Lucena position is a fundamental rook endgame configuration in which the side with the passed pawn has advanced it to the seventh rank and can force a win using a precise technique known as "building a bridge." In this position, the attacking king stands on the adjacent file at the seventh rank…
- Opening
Main line
The main line, in chess, is the sequence of moves considered the most theoretically sound and thoroughly analyzed in a given opening or variation, serving as the central reference in opening theory.
- Material
Major pieces
Major pieces in chess refer to the queen and the rook, as opposed to the minor pieces — the bishop and the knight.
- Strategy
Maneuver
A maneuver in chess is a sequence of coordinated moves — typically quiet ones — aimed at improving the position of one or more pieces without creating an immediate direct threat.
- Material
Material advantage
A material advantage in chess refers to the situation where one player has pieces of greater total value than their opponent, based on the standard point count system.
- Material
Material gambit
A gambit refers, in the strict sense, to the voluntary sacrifice of a pawn in the opening in order to gain concrete compensation: a lead in development, central control, or a strong initiative.
- Material
Material imbalance
A material imbalance occurs when both sides have different pieces on the board — whether in quantity, type, or both — such as a rook versus two minor pieces (a bishop and a knight), or a queen versus two rooks.
- Material
Material sacrifice
A material sacrifice in chess means deliberately giving up a piece or pawn — without immediate material compensation — in order to gain a concrete advantage: a decisive attack, the destruction of the opponent’s king shelter, a tempo gain, or lasting positional dominance.
- Tactics
Mating attack
A mating attack is an aggressive sequence of moves aimed directly at checkmating the opponent’s king, by coordinating pieces to surround it and eliminate all escape squares.
- Endgame
Mating pattern
A mating pattern is a recurring arrangement of pieces that delivers checkmate in a recognisable, repeatable configuration.
- Material
Minor pieces
In chess, the minor pieces are the knight and the bishop — as opposed to the major pieces, the rook and the queen.
- Pawn structure
Minority attack
The minority attack is a positional strategy in which a player advances a smaller group of pawns (the minority) into a larger enemy pawn group (the majority) on one flank, with the goal of creating structural weaknesses rather than breaking through.
- General
Move
A move in chess is the action of transferring a piece from one square to another according to the rules of the game, making it the fundamental unit of every chess game.
- Opening
Move order
Move order refers to the precise sequence in which moves are played during the opening phase, allowing a player to reach a target position while avoiding unwanted variations or opponent traps.
- General
Online rapid
Online rapid chess is a format played on the internet with a time control typically ranging from 10 to 30 minutes per player for the entire game.
- Opening
Open center
An open center is a pawn structure in which the central files (the d file and e file) are free of pawns, allowing pieces — especially rooks and the queen — to operate along them without obstruction.
- Pawn structure
Open structure
An open structure refers to a pawn configuration in which the central files are largely unobstructed, with few pawns remaining on the board and multiple open or half open files available for the major pieces.
- Opening
Opening preparation
Opening preparation refers to the work done away from the board to study and memorize opening move sequences, with the goal of entering a game with a knowledge advantage or at least a familiar position.
- Opening
Opening theory
Opening theory in chess refers to the body of moves, lines, and variations that have been analyzed, catalogued, and validated by players and analysts over centuries.
- Opening
Opening trap
An opening trap is a sequence of moves in the early game designed to lure the opponent into a specific mistake, resulting in a decisive advantage — often material gain or even a quick checkmate.
- Endgame
Opposite-colored bishops
Opposite colored bishops describes a situation where each side has one bishop travelling on squares of a different colour: one moves only on the light squares, the other only on the dark squares.
- Endgame
Opposition
Opposition is an endgame technique in which two kings face each other on the same rank or file, separated by an odd number of squares, with the player whose turn it is to move forced to give ground.
- Strategy
Outpost
An outpost is a stable square — typically in the center or enemy territory — where a piece, most often a knight, can be permanently stationed without being driven away by an opponent’s pawn.
- Tactics
Overloading
Overloading is a tactical motif that exploits a piece burdened with too many defensive duties at once — typically protecting two pieces or squares simultaneously — so that it cannot fulfill both responsibilities at the same time.
- Strategy
Overprotection
Overprotection is a strategic technique that consists of defending a key square or piece with more defenders than strictly necessary to hold it against the opponent’s attacks.
- Pawn structure
Passed pawn
A passed pawn is a pawn that has no opposing pawn in front of it on its own file or on either adjacent file, meaning no enemy pawn can block or capture it as it advances toward promotion.
- Endgame
Passed pawn endgame
A passed pawn in the endgame is a pawn with no opposing pawns on its file or on either adjacent file, whose promotion to a queen becomes the central objective of the endgame phase.
- Strategy
Passive piece
A passive piece is a piece that occupies a square where it has limited mobility, controls few important squares, and contributes little to its side’s active play.
- Material
Pawn
The pawn is the most numerous piece in chess: each player starts with eight, placed on the second rank (White) or the seventh rank (Black).
- Pawn structure
Pawn advance
A pawn advance is the act of pushing one or more pawns toward the opponent’s side of the board in order to gain space, open files, or create weaknesses in the enemy position.
- Pawn structure
Pawn break
A pawn break is a pawn move that opens or disrupts the pawn structure, creating open or semi open files for the pieces.
- Pawn structure
Pawn chain
A pawn chain is a structure in which two or more pawns of the same side are lined up diagonally, each one protecting the pawn directly in front of it.
- Pawn structure
Pawn chain base
The pawn chain base is the rearmost pawn in a pawn chain — a series of pawns protecting one another diagonally — and is structurally the most vulnerable link in that chain.
- Endgame
Pawn endgame
A pawn endgame is a phase of the chess game where both sides have only their king and pawns remaining, all other pieces having been exchanged off the board.
- Pawn structure
Pawn island
A pawn island is a group of pawns of the same color that is completely separated from the player’s other pawns by at least one empty file on each side, with no friendly pawn on an adjacent file.
- Pawn structure
Pawn lever
A pawn lever is a pawn move that directly attacks an opponent’s pawn in order to break open the pawn structure, alter which files become available, or free squares for one’s own pieces.
- Pawn structure
Pawn majority
A pawn majority is a situation where one side has more pawns than the opponent on one side of the board, making it possible to create a passed pawn through straightforward advances and exchanges.
- Pawn structure
Pawn minority
A pawn minority is a positional concept where one side has fewer pawns than the opponent on a given wing — typically two pawns against three.
- Pawn structure
Pawn tension
Pawn tension refers to a situation where two opposing pawns face each other diagonally and can mutually capture, creating a zone of tactical and strategic uncertainty on the board.
- Tactics
Perpetual check
Perpetual check is a tactical resource in which a player delivers an unending series of checks that the opponent’s king cannot escape, thereby forcing a draw by repetition.
- General
PGN
PGN (Portable Game Notation) is a standardized text format used to record and share chess games, capturing both the moves played and key game information such as players' names, date, and result.
- Endgame
Philidor position
The Philidor position is a fundamental defensive technique in rook and pawn vs.
- Strategy
Piece activity
Piece activity refers to a piece’s ability to influence as many squares as possible, participate meaningfully in the game, and generate concrete threats on the board.
- Strategy
Piece coordination
Piece coordination refers to the ability of a player’s pieces to work together harmoniously, supporting one another and combining their strengths toward a common objective.
- Material
Piece values
Piece values in chess are a point system used to quickly assess the material balance between the two sides.
- Tactics
Pin
A pin is a tactic that restricts an enemy piece by forcing it to stay on its square in order to protect a more valuable piece or square behind it, under threat of material loss.
- Strategy
Plan
A plan in chess is a coherent sequence of connected ideas that a player decides to pursue in order to improve their position or gain an advantage over their opponent.
- Strategy
Play on both flanks
Play on both flanks is a strategic concept that involves creating threats on both the kingside and the queenside, forcing the opponent to spread their defensive resources across the entire board.
- Strategy
Position evaluation
Position evaluation is the process by which a chess player analyses the board to determine which side holds an advantage, and what kind of advantage it is.
- Strategy
Positional advantage
A positional advantage in chess refers to a situation where one player holds a structural or qualitative superiority on the board, without necessarily having more material than the opponent.
- Strategy
Positional play
Positional play is a strategic approach to chess that focuses on gradually improving piece placement, creating long term weaknesses in the opponent’s position, and accumulating small advantages rather than seeking an immediate tactical conclusion.
- Tactics
Positional sacrifice
A positional sacrifice is the deliberate giving up of material — a pawn, a minor piece, or more — without an immediate tactical payoff, in exchange for lasting positional benefits: improved piece activity, control of key squares, prolonged initiative, or a superior pawn structure.
- General
Post-mortem analysis
Post mortem analysis is the critical review of a chess game carried out after it has ended, with the goal of identifying mistakes, missed opportunities, and key turning points.
- Strategy
Principle of two weaknesses
The principle of two weaknesses is a strategic concept in chess stating that one weakness in a position is often defensible, but two weaknesses on opposite sides of the board typically cannot both be held at the same time.
- Rules
Promotion rule
The promotion rule in chess states that any pawn reaching the opponent’s back rank — the 8th rank for White, the 1st rank for Black — must immediately be converted into another piece: a queen, rook, bishop, or knight.
- Strategy
Prophylaxis
Prophylaxis in chess is the art of anticipating and neutralizing the opponent’s plans before they become dangerous.
- Pawn structure
Protected passed pawn
A protected passed pawn is a passed pawn (meaning no enemy pawn can stop it on its file or on adjacent files) that is defended by another friendly pawn.
- Material
Queen
The queen is the most powerful piece in chess: it combines the movements of the rook (straight lines along files and ranks) and the bishop (diagonals), allowing it to reach up to 27 squares in a single move from the center of the board.
- Pawn structure
Queen pawn
The queen pawn is the pawn that starts on d2 for White (or d7 for Black), placed in front of the queen at the beginning of the game.
- Endgame
Queen vs pawn endgame
A queen vs pawn endgame is an endgame where one side has only a queen, while the other side has only a single advanced pawn — typically on the sixth or seventh rank — with no other pieces on either side.
- General
Queenside
The queenside refers to the left half of the chessboard from White’s perspective, covering the a, b, c, and d files — the side where the queen starts the game.
- Opening
Queenside castling
Queenside castling is a special chess move in which the king moves two squares toward the queenside — from e1 to c1 for White, or from e8 to c8 for Black — while the queenside rook moves to d1 (or d8 for Black), landing immediately to the king’s right.
- Tactics
Quiet move
A quiet move is a move that involves no capture, no check, and no immediately obvious threat — yet carries a decisive tactical or strategic idea.
- General
Rank
A rank, in chess, is a horizontal row of the chessboard, consisting of eight squares running from left to right.
- Rules
Rapid
Rapid chess is a time control format in which each player has between 10 and under 60 minutes for all their moves in a game.
- Opening
Rapid development
Rapid development is the opening principle of mobilizing all pieces to active squares as early as possible, before engaging in tactical or strategic operations.
- Opening
Repertoire
A chess repertoire is the set of openings and variations a player chooses to study and play consistently — one system for White and one or more responses for each of Black’s main replies — so that every game starts from familiar, well understood positions.
- Rules
Resignation
Resignation is the act by which a player concedes defeat during a game, without waiting for checkmate to occur.
- Strategy
Restriction
Restriction in chess is a strategic concept that involves limiting the mobility and activity of the opponent’s pieces — without necessarily capturing them — in order to gradually suffocate their position.
- Material
Rook
The rook is a major piece in chess that moves any number of squares in a straight line — horizontally or vertically — and cannot jump over other pieces.
- Endgame
Rook endgame
A rook endgame is a phase of the game where both sides have only rooks remaining (with or without pawns), all other pieces having been exchanged.
- Endgame
Rule of the square
The rule of the square is a visual calculation technique used in endgames to determine, without counting move by move, whether a king can catch a passed pawn before it promotes to a queen.
- Tactics
Sacrifice
A sacrifice in chess is a move in which a player deliberately gives up material — a pawn, a minor piece (knight or bishop), or a major piece (rook or queen) — in exchange for a different type of advantage: a decisive attack, a tempo gain, or a structurally superior position.
- Tactics
Scholar’s mate
Scholar’s mate is a four move checkmate in which White targets the f7 square — the weakest point in Black’s starting position — using the queen and a bishop to deliver an instant finish.
- Strategy
Simplification
Simplification is a strategic operation that consists of reducing the number of pieces on the board, typically through exchanges, in order to consolidate an existing advantage or neutralize the opponent’s counterplay.
- Tactics
Skewer
A skewer in chess is a tactical device in which an attacking piece targets a high value enemy piece, forcing it to move out of the line of attack — and exposing a less valuable piece behind it, which can then be captured.
- Tactics
Smothered mate
A smothered mate is a checkmate delivered by a knight, in which the mated king is completely surrounded — or "smothered" — by its own pieces and has no escape square.
- Strategy
Space advantage
A space advantage in chess refers to the situation where one side controls more squares on the board than the opponent, typically through advanced pawns that restrict the mobility of the enemy pieces.
- Rules
Stalemate
Stalemate in chess is the situation where the player whose turn it is to move has no legal move available, yet their king is not in check.
- Strategy
Strategic exchange
A strategic exchange in chess refers to the deliberate trading of a piece for an opponent’s piece of nominally equal (or even slightly higher) value, with the goal of gaining a lasting positional advantage rather than an immediate material benefit.
- Strategy
Strong square
A strong square is a square that the opponent’s pawns can no longer attack, allowing a piece to settle there permanently without risk of being driven away by a pawn.
- Opening
Symmetry
Symmetry in chess refers to a position where both sides mirror each other’s moves, creating an identical or near identical structure on both halves of the board, reflected across the horizontal axis between the two camps.
- Opening
System
A system in chess is a set of opening moves built around general principles — rather than deep theoretical memorization — that White or Black applies regardless of the opponent’s choices, with the goal of reaching a playable and coherent position.
- Tactics
Tactical initiative
Tactical initiative in chess is the ability to generate a continuous sequence of concrete, calculable threats that force the opponent into a passive or reactive stance, leaving them little time to pursue their own plans.
- Tactics
Tactical motif
A tactical motif is a recurring piece configuration that allows a player to win material, gain a decisive advantage, or deliver checkmate through a calculated sequence of moves.
- Tactics
Tempo
In chess, a tempo refers to a single unit of time — one move.
- Material
The exchange
The exchange, in chess, refers to the material difference between a rook and a minor piece (knight or bishop).
- Endgame
Theoretical draw
A theoretical draw is a chess position in which, no matter how both players continue, the game cannot end in checkmate: it will inevitably result in a draw with perfect play from both sides.
- Opening
Theoretical novelty
A theoretical novelty in chess (often simply called a novelty , abbreviated TN or N in annotations) is a move played within a known opening that departs from all previously recorded theory, introducing an idea that has not appeared in databases or reference works.
- Tactics
Threat
A threat in chess is a move or plan that, if left unanswered, will result in material gain, checkmate, or a decisive advantage for the attacking side.
- Rules
Time control
Time control in chess refers to the amount of time each player is given to make their moves during a game, as tracked by a chess clock.
- General
Time trouble
Time trouble refers to the critical situation where a player is running dangerously low on the clock, to the point where time management becomes as decisive as the quality of the moves played.
- Rules
Touch-move rule
The touch move rule in chess states that a player who intentionally touches one of their own pieces must move it, and if they touch an opponent’s piece, they must capture it — provided the capture is legal.
- Opening
Transposition
A transposition is the act of reaching an identical chess position through a different move order than the one typically associated with a given opening.
- Tactics
Trap
A trap in chess is a sequence of moves designed to lure the opponent into a specific mistake, typically by presenting an opportunity that appears attractive but is actually a tactical illusion.
- Endgame
Triangulation
Triangulation is an endgame technique in which a king takes a three square detour — tracing a triangle — to transfer the move to the opponent, placing them in zugzwang (a situation where any move worsens their position).
- General
Turn to move
"Having the move" — in French, le trait — means it is your turn to move a piece on the board.
- Endgame
Two bishops mate
The two bishops mate is an endgame technique that forces checkmate using two bishops in coordination with the king, without the support of additional active pieces.
- Opening
Variation
A variation in chess is a specific, named sequence of moves that branches off from an opening, defining one particular path among all the possible continuations available in the early phase of a game.
- Tactics
Waiting move
A waiting move is a deliberately neutral move whose sole purpose is to transfer the turn to the opponent, forcing them to play in a position where any move they make is unfavourable.
- Pawn structure
Weak pawn
A weak pawn is a pawn that cannot be defended by another pawn and therefore becomes a permanent target for the opponent’s pieces.
- Strategy
Weak square
A weak square in chess is a square that can no longer be defended by a pawn of the side that owns it, allowing the opponent to occupy it with a piece that cannot be driven away.
- Strategy
Wing expansion
Wing expansion is a strategic plan that involves advancing pawns on one side of the board — the kingside or the queenside — in order to gain space, open files, and generate concrete threats against the opponent’s position.
- Tactics
X-ray
The X ray (also called X ray attack) is a tactical motif in which a piece exerts pressure through an opposing piece, targeting a valuable piece or square located directly behind it on the same line.
- Tactics
Zugzwang
Zugzwang is a chess situation in which the player whose turn it is to move is forced to make a move that worsens their own position — and would clearly prefer to pass.
- Tactics
Zwischenzug
The zwischenzug (German for "in between move") is an unexpected move inserted into an apparently forced sequence — such as a series of exchanges — before responding to the opponent’s last move.