Check — what it means in chess
A direct attack on the king that must be answered at once.
A direct attack on the king that must be answered at once.
[[board startfen="rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1" caption="Check: the bishop attacks the king along the open diagonal, and every other plan on the board is suspended. The move in reply must answer the attack — block, capture, or flee — or it is not legal at all." pgn="e4 e6 d4 Bb4+" notes="The one threat in chess that cannot be postponed. White opens classically. The French — and the f8 bishop's diagonal quietly opens with it. White takes the full center — — and the check lands: Bb4+, striking the king along the b4-e1 diagonal. The + in the notation announces what the rules enforce: White's next move MUST answer this attack. Here the geometry allows blocking (c3, or a piece to d2) or a king step; nothing can capture the bishop. The three escapes — block, capture, flee — are the complete menu, always, and when all three fail the word changes from check to checkmate."]]
Check is an attack on the king, and it carries the only absolute priority in chess: the checked player's next move must answer it — the rules refuse any move that leaves the king attacked. Three answers exist, and only three: block the attacking line with a piece, capture the attacker, or move the king to a safe square. Every check in every game resolves into that menu, and when all three items fail, the check is checkmate and the game is over.
The demonstration above shows the mechanism and its notation — the + suffix announcing the attack — and a common geometry: a diagonal check that can be blocked or walked away from but not captured. The menu's contents vary by position, which is the tactical heart of the matter: a knight's check can never be blocked (nothing stands on a knight's path), a contact check from an adjacent defended piece can only be answered by flight, and a double check — two attackers at once — forces the king to move, since no single block or capture can answer two lines.
The Endgame Society glossary defines more than 240 chess terms — rules, notation, tactics, strategy, pawn structures, endgames, and openings — in language a beginner can act on rather than dictionary shorthand.