Chess glossary

Published 20 October 2026

Chess has a vocabulary of its own, some of it borrowed from Persian, French and German. This glossary explains the terms used on this site and in most chess books and videos, in plain language. Where a term has a page here that covers it in depth, the entry says so. For the rules themselves, the rules guide is the place to start.

Values given for pieces (pawn 1, knight and bishop about 3, rook about 5, queen about 9) are the conventional teaching scale. They are a rough guide for trades, not a law; position often matters more.

A

Algebraic notation

The standard way to write moves, using a piece letter and a square name, such as Nf3 or exd5. It is the notation in this site's move list.

B

Back-rank mate

Checkmate by a rook or queen along the first or eighth rank, when the king is trapped behind its own unmoved pawns. A pawn move such as h3 (luft) prevents it.

Bad bishop

A bishop hemmed in by its own pawns standing on its colour. It is often still a useful defender, but it has fewer squares than a good bishop.

Blunder

A move that loses material or the game outright, usually to a simple tactic. Annotators mark it with ??.

C

Candidate moves

The short list of moves worth considering in a position. Strong players pick two or three candidates and compare them, rather than looking at every legal move.

Castling

The move in which the king goes two squares toward a rook and the rook jumps to the other side of it. It is legal only if neither has moved, the squares between are empty and the king does not pass through check.

Check

An attack on the king. The player in check must end it at once by moving the king, capturing the attacker or blocking.

Checkmate

A check that cannot be answered. It ends the game. The word comes from the Persian shah mat.

Connected rooks

Rooks on the same rank or file with nothing between them, so that each protects the other. Connecting them is a sign that the opening is complete.

D

Desperado

A piece that is lost anyway and sells itself as dearly as possible, usually by capturing something before it is taken.

Development

Moving pieces off their starting squares toward useful posts. In the opening it matters more than winning a pawn.

Discovered attack

Moving one piece so that a piece behind it suddenly attacks along the line it opened. If the hidden piece gives check, it is a discovered check.

Double check

A check by two pieces at once, usually from a discovered check. The only legal answer is a king move.

Doubled pawns

Two pawns of the same colour on one file. They cannot defend each other, which tends to make them weak in endgames.

E

En passant

The special pawn capture available immediately after an enemy pawn moves two squares and lands beside yours. You capture it as if it had moved one square.

Endgame

The final phase, with few pieces left. Kings become active and passed pawns become decisive.

Exchange

A trade of pieces. 'Winning the exchange' means giving a bishop or knight for a rook.

F

Fianchetto

Developing a bishop to b2 or g2 (b7 or g7 for Black) after moving the knight's pawn one square, so the bishop controls the long diagonal.

File

A vertical column of the board, named a to h. An open file has no pawns; a half-open file has only the opponent's.

Fork

One piece attacking two or more enemy pieces at once. Knights and pawns are the classic forking pieces. See this explained in depth.

G

Gambit

An opening in which a pawn or piece is offered for time or position. The Queen's Gambit is the best known. See this explained in depth.

H

Hanging piece

A piece that is attacked and not defended, which can be taken for free.

I

Isolated pawn

A pawn with no friendly pawns on the adjacent files. It cannot be protected by a pawn, and the square in front of it is a good post for the opponent.

J

J'adoube

French for 'I adjust'. Said in over-the-board play before touching a piece only to straighten it, so that the touch-move rule does not apply.

K

Kingside

The half of the board on the e to h files, where the kings start. Castling there is called castling short.

L

Luft

German for 'air'. A pawn move in front of the castled king that gives it an escape square, typically h3 or h6.

M

Major pieces

Rooks and queens. A rook is worth about five pawns, a queen about nine.

Middlegame

The phase between the opening and the endgame, when most pieces are still on and plans and tactics decide the game.

Minor pieces

Bishops and knights. Each is worth roughly three pawns in the usual scoring.

O

Opposition

In king endings, the situation where the two kings face each other with one square between them. The side not to move holds the opposition and usually gets its way. See this explained in depth.

Outpost

A square in the opponent's half that their pawns can no longer attack. A knight on an outpost is often stronger than a rook. See this explained in depth.

P

Passed pawn

A pawn with no enemy pawn in front of it on its own file or the files beside it. Only pieces can stop it from promoting.

Perpetual check

A series of checks the defender cannot escape, which results in a draw by repetition.

Pin

An attack on a piece that cannot move without exposing a more valuable piece behind it. If the piece behind is the king, the pinned piece may not move at all. See this explained in depth.

Ply

A single move by one player. A full move in notation is two plies, one by White and one by Black. The move list on this site counts plies.

Promotion

Replacing a pawn that reaches the last rank with a queen, rook, bishop or knight. Promoting to anything other than a queen is called underpromotion.

Q

Queenside

The half of the board on the a to d files. Castling there is called castling long.

R

Rank

A horizontal row of the board, numbered 1 to 8 from White's side.

Resign

To concede the game before checkmate. On this site the Resign button appears during online games.

S

Sacrifice

Deliberately giving up material for an attack, a better position or a forced win.

Skewer

An attack along a line on a valuable piece, which must move and expose a less valuable piece behind it to capture. It is the reverse of a pin. See this explained in depth.

Smothered mate

A checkmate by a knight against a king surrounded by its own pieces. The Blackburne Shilling trap ends in one. See this explained in depth.

Stalemate

A position in which the player to move has no legal move and is not in check. It is a draw. See this explained in depth.

T

Tempo

A unit of time, one move. Gaining a tempo means making a useful move that also forces the opponent to respond, such as developing with an attack on a piece.

Threefold repetition

A draw that occurs when the same position appears three times with the same player to move and the same rights.

Touch-move

The over-the-board rule that a player who deliberately touches a piece must move it if it has a legal move. It does not apply to clicking on a screen.

U

Underpromotion

Promoting a pawn to a rook, bishop or knight instead of a queen, usually to avoid stalemate or to give a knight check.

Z

Zugzwang

German for 'compulsion to move'. A position in which any move worsens your position, so you would rather pass. It is common in king and pawn endings.

Zwischenzug

German for 'in-between move'. An unexpected move, often a check or threat, played before making the obvious recapture.

Missing a term you have seen on another site or in a book? Write to the address on the contact page and it may be added. The history page explains where some of these words came from.