Absolute pin:A pin against the king, called absolute because the pinned piece cannot legally move as it would expose the king to check.
Active:Describes a piece that is able to move or control many squares.Pieces are most active in the centre.
Adjournment:Suspension of a chess game with the intention to continue at a later occasion.Games can be adjourned because it has been long time or one or both players being unable to play anymore.
Adjust/j'adoube:To adjust the position of a piece on its square without being required to move it. Adjustment can only be done when it is the player's move and the adjustment is preceded by saying "I adjust" or "j'adoube".
Advanced pawn:A pawn that is on the opponent's side of the board (the fifth rank or higher). An advanced pawn may be weak if it is overextended, lacking support and difficult to defend, or strong if it cramps the enemy by limiting his mobility. An advanced passed pawn that threatens to promote can be especially strong.
Alekhine's gun:A formation where a queen assists two rooks on the same vertical line.
Algebraic notation:The standard way to record a chess game using coordinates for the squares.
Analysis:Breaking a position into iterations or most likely moves.
Annotation:Commentary on a game using a combination of written comments, chess symbols or notation.
Antipositional:A move or a plan that is not in accordance with the principles of posititional play. Antipositional is used to describe moves that are part of an incorrect plan rather than a mistake made when trying to follow a correct plan. Antipositional moves are often pawn moves, since pawns cannot move backwards to return to squares they have left.
Arbiter:A tournament official who arbitrates disputes and performs other duties such as keeping the score when players are under time pressure.
Armageddon:A game which White must win to win the match, but which Black only needs to draw to win the match. White has more time than black: the discrepancy can vary, but in FIDE World Championships, White has six minutes, while Black only has five. Typically used in playoff tie-breakers where shorter blitz games have not resolved the tie.
Artificial castling:Refers to a manoeuvre of several single moves by the king and a rook where they end up as if they had castled.
Attack:An aggressive move or strategy.
Automaton:A self-operating chess-playing machine. Popular attractions in the 18th and 19th centuries, most of these devices were hoaxes under the control of a human player. The most famous chess-playing automaton was The Turk.