Chess glossary: 70 terms in plain words

Castling

The only move that shifts two pieces at once: the king travels two squares towards a rook and the rook jumps over it. Not allowed if the king or that rook has moved, if the king is in check, or if it would cross an attacked square.

En passant

A pawn that has just advanced two squares from its starting position may be captured by an adjacent enemy pawn as though it had moved one. The right exists only immediately, on the very next move.

Promotion

A pawn reaching the last rank must become a queen, rook, bishop or knight. Staying a pawn is not an option, and the number of queens on the board is not limited.

Check

An attack on the king. Responding is compulsory: move away, block, or capture the attacker.

Checkmate

A check with no defence. The game ends immediately in a win.

Stalemate

The side to move has no legal move but its king is not in check. An immediate draw, regardless of material.

Touch-move

Touch your own piece and you must move it; touch an enemy piece and you must capture it if legally possible. To adjust a piece you must say «I adjust» first.

Perpetual check

A series of checks the king cannot escape. It usually leads to a draw by repetition.

Threefold repetition

If the same position occurs three times with the same side to move and the same options available, a draw may be claimed.

Fifty-move rule

If fifty consecutive moves pass with no capture and no pawn move, either side may claim a draw.

More detail - basic checkmates and stalemate.

Fork

One piece attacking two or more at once. Knights and pawns do it most often.

Pin

A piece cannot move because something more valuable stands behind it. Only queen, rook and bishop can pin.

Double attack

Any simultaneous threat in two directions. A fork is a special case.

Discovered attack

A piece moves off a line and opens the fire of a long-range piece behind it. Two moves for the price of one.

Double check

Check from two pieces at once. The only legal reply is a king move: blocking and capturing are both impossible.

Deflection

Forcing a defender away by giving it a more urgent task, usually with check.

Decoy

Forcing a piece onto a square where a fork or a mate awaits. Usually by a sacrifice that cannot be declined.

Overloading

One piece defending two objects at once - which means it defends neither properly.

Zwischenzug

An in-between move: an unexpected threat inserted into an expected sequence of exchanges.

Sacrifice

Giving up material deliberately for attack, initiative or a positional gain.

Combination

A forced sequence involving a sacrifice that leads to a concrete gain: mate or material.

Smothered mate

Mate by a knight against a king completely boxed in by its own pieces. The classic finish involving a double check.

Windmill

A repeating series of discovered checks in which one piece returns again and again to collect material.

Blunder

A gross error: a piece left hanging or a threat missed. The main cause of amateur losses.

Worked through with examples - tactics for beginners.

Centre

The four central squares and the zone around them. Controlling them gives pieces mobility.

Tempo

One move as a unit of time. To lose a tempo is to make a move that adds nothing.

Initiative

The state of setting the threats while the opponent has to answer them.

Development

Bringing pieces off their starting squares in the opening. Falling behind in development is a classic route to a quick loss.

Outpost

A square in the opponent's half where you can post a piece and from which no pawn can chase it away.

Weak square

A square that can no longer be defended by a pawn. An ideal home for an enemy piece.

Isolated pawn

A pawn with no friendly pawns on adjacent files. Weak in the endgame, but a source of activity in the middlegame.

Doubled pawns

Two friendly pawns on the same file. Usually a weakness, occasionally a useful open file.

Backward pawn

A pawn left behind its neighbours and unable to catch up without loss. A permanent target.

Passed pawn

A pawn with no enemy pawns ahead of it, on its own file or on the adjacent ones.

Pawn chain

Pawns defending one another diagonally. The usual way to attack one is at its base.

Fianchetto

Developing a bishop onto a long diagonal after advancing the adjacent rook's or knight's pawn one square.

Open file

A file with no pawns on it. The main working route for rooks.

Bishop pair

Two bishops against bishop and knight or two knights. On an open board it counts as a small but lasting plus.

The exchange

The difference between a rook and a minor piece. To «win the exchange» is to give up a bishop or knight for a rook.

Compensation

What you get in return for material given up: attack, initiative, active pieces.

Opposition

Kings facing each other on a line with one square between them. Whoever must move has to give way.

Zugzwang

A position where every move worsens things but passing is not allowed. The main winning mechanism in pawn endgames.

Rule of the square

A way to see instantly whether the king catches a running pawn, without calculating.

Key squares

Squares in front of a pawn which, once occupied by your king, promote it against any defence.

Outside passed pawn

A passed pawn on the far wing. It drags the enemy king away while your king eats pawns elsewhere.

Fortress

A structure the weaker side holds regardless of the opponent's material advantage, securing a draw.

Lucena position

The key winning method in a rook endgame with an extra pawn, known as «building a bridge».

Philidor position

The key drawing method in a rook endgame a pawn down: defence along the third rank.

Explained with positions on a board - pawn endgames.

Opening

The first phase: developing pieces and fighting for the centre, usually the first ten to fifteen moves.

Middlegame

The middle phase, where plans are carried out and most of the tactics happen.

Endgame

The final phase with few pieces left. The king turns from an object of defence into an active piece.

Gambit

An opening sacrifice, usually of a pawn, in return for fast development and initiative.

Variation

A specific sequence of moves, either in an opening or in your calculation.

Novelty

A move never previously played in a known position.

Time control

How much time is given for a game. It defines the type of event: classical, rapid or blitz.

Increment

Seconds added for each move made. «5+3» means five minutes plus three seconds per move.

Flag

The moment the time runs out. To «lose on time» is to lose by the clock.

Swiss system

Opponents are matched by score each round. The standard system for amateur events.

Round robin

Everyone plays everyone. Maximally fair but only workable for small fields.

Knockout

Matches with elimination: the loser goes out. Requires a tie-break when a match is level.

Pairing

Drawing up the pairs for the next round. In a Swiss it is done by software under strict rules.

Bye

The point awarded to a player left without an opponent when the field is odd.

Buchholz

A tie-break: the sum of your opponents' scores. It measures how hard the road was.

Performance rating

The rating that corresponds to the result you actually showed in an event, regardless of your current rating.

Elo rating

A numerical measure of playing strength, updated after each rated game by comparing the result with the expectation.

Title

An international rank such as Grandmaster or International Master, earned through norms and a rating threshold.

Norm

A result of the required level needed for an international title. Several are required.

Scoresheet

The form on which the moves are written down. Compulsory in classical play, not in blitz.

Appeal

A challenge to an arbiter's decision, heard by the event's appeals committee.

Regulations

The main document of an event: dates, system, time control, prizes and how places are decided.

More detail - tie-breaks, the Buchholz score, how many rounds a Swiss needs.