A single piece menaces two or more enemy pieces at once. Against the best defence they cannot all be saved, so the move wins material.
Cite this entryChessGrammar (2026). Fork. In: ChessGrammar: A reference for chess concepts, Tactics grammar, edition v3.0. Entry cg:fork@1. https://chessgrammar.com/motifs/tactics/fork
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Start position
the definition and its boundary
Nd5
The knight lands on d5 and menaces two rooks at once, on c7 and f4. They cannot both be saved, and the best defence Rf7 concedes the exchange on f4. One piece, two effective targets and a gain held against the best defence make this exactly a Fork.
7k/1pr5/8/8/4Pr2/2N4P/6PK/8 w - - 0 1Nd5
A Fork requires two conditions. One piece must attack at least two effective targets, and at least one target must remain lost after the best defence. A single vulnerable target may instead be Hanging or Trapped. A position in which every target can be saved is not a Fork. In the counter-example shown here, only one target remains.
From d5 the knight now attacks a single enemy piece, the rook on c7. With fewer than two targets attacked, no fork exists. One attacked piece is a matter of Hanging or Trapped, never of Fork.
7k/1pr2r2/8/8/4P3/2N4P/6PK/8 w - - 0 1the variants
The forms below are grouped by the feature they describe. A feature may have no separate named form. Open a form to read its criteria and see its examples.
Knight Forkknight double attack
The forking piece is a knight.
Pawn Forkpawn wedge
The forking piece is a pawn.
Queen Forkmulti-linear fork
The forking piece is a queen.
Bishop Forkdiagonal double attack
The forking piece is a bishop.
Rook Forkorthogonal double attack
The forking piece is a rook.
King Forkking double attack
The forking piece is the king.
Royal Forkking-queen fork
King and queen among the effective targets.
Family Forkfull house · triple fork
The king and the queen are among the targets, with at least one rook or minor piece.
King-Rook Fork
King and rook among the effective targets, no queen.
Queen-Rook Fork
Queen and rook among the effective targets, no king.
Double Fork
Exactly two effective targets.
Triple Fork
Exactly three effective targets.
Absolute Forkcheck fork
The king is among the targets.
Relative Forkmaterial fork
No king is among the targets.
forms the literature names but the taxonomy does not carry as entries of their own
Geometric Forktriangulation · loose-piece double attack
Outlined — no formal discriminator published.
Discovered Forkdiscovery fork
Produced as a co-tag: Fork and Discovered Attack are emitted together. This form has no predicate of its own.
Blind-Spot Forkbackward knight fork · retrograde fork
Descriptive — catalogued for teaching, without a formal predicate.
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