The Encyclopaedia of Chess Openings (ECO) is a reference work describing the state of opening theory in chess, originally published in five volumes from 1974 to 1979 by the Serbian company Šahovski Informator. It is currently undergoing its fifth edition. ECO may also refer to the opening classification system used by the encyclopedia.
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Chess is a board game for two players. It is sometimes called international chess or Western chess to distinguish it from related games such as xiangqi and shogi.
Part of a Staunton chess setLeft to right: white king, black rook, black queen, white pawn, black knight, white bishop
Setup at the start of a chess game
A digital chess clock
Public chess tables in the Jardin du Luxembourg, Paris