Chess Glossary: the terms you will hear in every game

Chess vocabulary arrives fast: someone says your knight is pinned, that the position is zugzwang, or that the game ended on the flag. Here are the terms you will actually hear at the board, grouped by subject and defined in one sentence each, with two diagrams for the ideas nobody absorbs from reading alone.

Rules terms

• Check: the king is under attack and you must deal with it on your next move, by stepping away, blocking or capturing.
• Checkmate: the king is in check and no legal move saves it, so the game ends right there.
• Stalemate: it is your turn, your king is not in check and you have no legal move at all, which is a draw.
• En passant: a pawn that advances two squares and lands beside an enemy pawn can be captured as though it had moved only one.
• Promotion: a pawn reaching the far rank becomes a queen, rook, bishop or knight, with no limit on identical pieces.
• Castling: the only move that shifts two pieces, allowed when king and rook have never moved, the squares between are empty and the king never crosses an attacked square.
• Touch move: over the board, a piece of yours that you touch is a piece you must move, and to straighten one you say "I adjust" first.

Tactical terms

• Fork: one piece attacks two targets at once, and the knight is the specialist because it reaches squares no other piece covers.
• Pin: a piece cannot leave a line because something more valuable stands behind it, and if that is the king, moving is illegal.
• Skewer: a pin turned around, with the valuable piece in front, forced to move so the one behind it drops.
• Discovered attack: you move one piece and the attack comes from whatever stood behind it, so one move makes two threats.
• Zwischenzug: the in-between move, a check or bigger threat you slip in before the obvious recapture.
• Zugzwang: having the move is the problem, because every legal move worsens your position and passing does not exist.
• Desperado: a doomed piece selling itself as expensively as possible, grabbing something before it falls.

Black has five legal moves and all of them abandon the pawn's file: after 1...Kd7 2.Kf6 the white king walks around the black one, escorts the pawn and promotes. Flip the turn and it is White who has to concede the opposition: 1.Kd5 Kd7 2.e5 Ke7 3.e6 Ke8 4.Kd6 Kd8 5.e7+ Ke8 6.Ke6 leaves Black stalemated. Half a point of difference, and the only variable is whose turn it is.

Positional terms

• File: a vertical line, a through h, where rooks and queens do their best work.
• Rank: a horizontal line, 1 through 8, and the eighth is where back rank mate lives.
• Diagonal: the bishop's slanted line, the longest two being a1-h8 and h1-a8.
• Outpost: an advanced square in enemy territory that no enemy pawn can ever attack.
• Tempo: the unit of time in chess is one move, and gaining a tempo means developing while making a threat.
• Initiative: being the side that makes the threats and chooses what the game is about.
• Prophylaxis: playing against your opponent's idea before it ever happens.
• Space: the territory your pawn chain guarantees, and its absence is why the cramped side trades pieces.
• Opposition: kings facing each other with an odd number of squares between them, where the side not moving holds it.
• Fianchetto: putting a bishop on b2, g2, b7 or g7 after nudging the pawn in front of it.
• Gambit: offering material in the opening, almost always a pawn, in return for development, center or initiative.

Neither bishop occupies the center and both of them press on it from a distance: that is the idea of the fianchetto, the longest diagonal on the board for one pawn move and one bishop move. The price is the hole the pawn left next to the king, which is why trading that bishop after castling short is usually a bad deal.

Practical and clock terms

• Time control: how much thinking time each player gets, written as base time plus increment, such as 5+3.
• Blitz: games of 3 to 5 minutes per player, with time for a plan but not for calculation.
• Rapid: the middle band, roughly 10 to 30 minutes per player.
• Classical: an hour or more per side, the format of official tournaments.
• Increment: the seconds added to your clock after every move you play.
• Flag: to lose by running out of time, named after the little flag on analog clocks.
• Blunder: the big mistake, the one that hands over a piece or the game in one move.
• Resign: to concede before being mated, which nobody is obliged to do in a friendly game.
• Draw offer: proposing a draw after making your move and before pressing the clock.
• Rating: a number estimating your strength from your results, almost always through the Elo system.
• FIDE: the international chess federation, owner of the official rules, the rating list and the FM, IM and GM titles.

The pairs people mix up

• Pin and skewer: in a pin the valuable piece is behind, in a skewer it is in front.
• Zugzwang and zwischenzug: one is a shortage of options, the other is playing something else before the expected move.
• File and rank: files are vertical and carry letters, ranks are horizontal and carry numbers.
• Stalemate and threefold repetition: stalemate happens on its own, repetition needs the same position three times with the same side to move.