Chess terminology,
without ambiguity.

A pin to the king. The pinned piece may not move in a way that exposes its king to check, although a rook, bishop or queen may sometimes move along the line while continuing to shield the king.

The extent to which a piece has useful squares, targets or influence. Active pieces normally have more practical effect than passive ones.

The standard system for recording chess moves using piece letters and board coordinates, such as Nf3 or Rxe5+.

A mating pattern in which a knight controls two escape squares while a rook or queen gives mate along the edge of the board, usually after the adjacent file is opened.

A mating pattern in which a rook gives check beside a cornered king while a knight protects the rook and covers the remaining escape square.

A tactic that draws a piece, often the king, onto a square where another tactic becomes possible. It is closely related to a decoy.

Checkmate delivered by a rook or queen along the opponent’s back rank when the king is trapped by its own pieces, usually pawns.

A pawn that cannot safely advance and cannot be protected by another pawn, often becoming a long-term target.

A bishop restricted by its own pawns, particularly when those pawns occupy squares of the same colour as the bishop.

Two or more pieces aligned on the same rank, file or diagonal to increase pressure along that line.

The advantage or characteristic of retaining both bishops, which can work together on both colours and often become stronger in open positions.

A fast time control in which each player has ten minutes or less for the entire game, according to the FIDE Laws of Chess.

Placing a piece, often a knight, directly in front of an enemy pawn to stop its advance and restrict the position.

A serious mistake that substantially worsens the position, commonly by losing material, allowing mate or overlooking a decisive tactic.

The process of analysing possible moves and replies in sequence before choosing a move.

One of a small number of plausible moves selected for serious calculation before a decision is made.

A move that removes an opponent’s piece or pawn from the board by occupying its square.

An opening beginning 1.e4 c6, usually followed by ...d5, in which Black challenges the centre with a solid pawn structure.

A single move involving the king and a rook that normally improves king safety and activates the rook. It is legal only when the relevant conditions in the Laws of Chess are satisfied.

Influence over the central squares, particularly e4, d4, e5 and d5, using pawns and pieces.

An attack on the king. The player in check must make a legal move that removes the check.

Enough separation between a rook and the enemy king for the rook to give checks without being driven away, especially in rook endgames.

A position in which a king is in check and no legal move can remove the check. The game ends immediately.

A sacrifice that vacates a line or square so another piece can use it.

A position with locked pawn chains and few open lines, where manoeuvring and prepared pawn breaks are normally more important than immediate line-piece activity.

A calculated forcing sequence, usually containing tactical motifs and sometimes a sacrifice, that achieves a concrete result.

Positional or tactical advantages received in return for a material concession, such as activity, initiative, king safety or pawn structure.

The process of turning an advantage into a win while controlling counterplay and avoiding unnecessary risk.

An attack launched in response to the opponent’s attack, intended to create threats rather than defend passively.

Active play that creates threats or practical problems for the opponent, particularly when defending an inferior position.

A position in which one piece is pinned along two different lines at the same time.

A tactic that induces a piece onto a particular square where it becomes vulnerable or allows another tactic.

A tactic that forces a defending piece away from a square, line or piece it must protect.

A piece that is certain to be lost but first captures material or creates another useful forcing action.

Bringing pieces from their starting squares to useful, active squares, normally as an opening priority.

A straight line of same-coloured squares running at an angle across the board.

An attack revealed when one piece moves out of the line of a bishop, rook or queen.

A discovered attack in which moving one piece uncovers a check from another piece.

One move or sequence that attacks two targets at the same time. A fork is one form of double attack.

A check delivered by two pieces at once. The checked king must move because blocking or capturing only one checker cannot answer both attacks.

Two friendly pawns on the same file, usually created by a capture. They may be weak, but can also control useful squares or open lines.

A completed game in which neither player wins. A draw may arise through stalemate, agreement, repetition, the fifty-move rule, dead position or other rules.

A Queen’s Gambit trap in which Black inserts ...Bb4+ before the expected recapture and then wins material through a forcing sequence.

A special pawn capture available only immediately after an opposing pawn advances two squares and passes a square controlled by the capturing pawn.

A French expression meaning that a piece or pawn is exposed to capture.

The final phase of a game, usually with reduced material, in which king activity, pawn promotion and technical positions become especially important.

Chess software that analyses positions and moves. Engines are useful for verification but do not replace a player’s explanation of why a move works.

A legal square to which a king can move to evade check or avoid a mating net.

An assessment of a position based on material, king safety, pawn structure, piece activity, space, initiative and concrete tactical factors.

Either a sequence in which material is traded, or the material difference between a rook and a bishop or knight, depending on context.

The deliberate surrender of a rook for a bishop or knight in return for positional or tactical compensation.

Forsyth–Edwards Notation: a compact text format that records a complete chess position, including side to move and relevant rule information.

Developing a bishop to b2, g2, b7 or g7 after moving the adjacent knight pawn.

One of the board’s eight vertical columns, identified by the letters a to h.

An opening trap in which a knight on g4 or g5 is offered so that accepting it opens the h-file for an attack on the castled king.

A move that severely limits the opponent’s replies, typically a check, capture or direct threat.

A double attack in which one piece attacks two or more enemy targets at the same time.

A defensive piece configuration that the stronger side cannot breach, making progress impossible and normally securing a draw.

An opening beginning 1.e4 e6, normally followed by ...d5, in which Black challenges White’s centre and accepts a space disadvantage for a solid structure.

A sharp Italian Game line in which White sacrifices a knight on f7 after Black’s inaccurate ...Nxd5, exposing the black king to attack.

An opening in which material, usually a pawn, is offered to gain development, initiative or another form of compensation.

The thematic bishop sacrifice Bxh7+ or ...Bxh2+ used to expose a castled king, normally with a knight and queen ready to join the attack.

A sharp gambit in the Four Knights Game in which White sacrifices a knight with 4.Nxe5 to gain time and central space by advancing the pawns.

A piece that is attacked, insufficiently defended and available to capture. This is narrower than an undefended piece, which need not be attacked.

A rook or queen. The equivalent expression major piece is also used.

Making a move while relying on the opponent to overlook the best reply, rather than verifying the move against accurate resistance.

The ability to make threats and force the opponent to respond, thereby influencing the course of play.

A tactic that places a piece between two connected pieces, interrupting an attacking or defensive line.

A pawn with no friendly pawn on either adjacent file, so it cannot be protected by another pawn.

An opening beginning 1.e4 e5 2.Nf3 Nc6 3.Bc4, developing rapidly and applying pressure to f7.

Squares whose occupation by the attacking king guarantees promotion of a pawn in certain king-and-pawn endings.

The degree to which a king is protected from checks, mating attacks and forcing lines.

An endgame containing kings and pawns but no other pieces, where opposition, key squares and pawn races are central themes.

A defence to 1.d4 in which Black commonly develops with ...Nf6, ...g6, ...Bg7 and ...0-0 before challenging White’s centre.

A practical queen-and-king checkmate method: place the queen a knight’s move from the enemy king to mirror and restrict it, while taking care not to cause stalemate.

A checkmating method in which two rooks, or a rook and queen, alternately check and restrict a bare king rank by rank or file by file.

A trap in the Albin Countergambit featuring a forcing advance of the d-pawn and a notable knight underpromotion.

An opening trap in which a seemingly pinned knight moves, allowing the queen to be captured because the resulting attack produces checkmate.

A queen’s-pawn opening in which White commonly develops the dark-squared bishop early and uses a setup involving Nf3, e3, c3 and Bd3.

A bishop, rook or queen: a piece that attacks along ranks, files or diagonals until another piece blocks the line.

A fundamental winning rook-and-pawn versus rook position in which the stronger side commonly uses the bridge-building method to shelter its king from checks.

An escape square created for the king, usually by moving a pawn in front of a castled king to reduce back-rank mating danger.

The pieces and pawns held by each side, often compared using approximate values to identify a material advantage or deficit.

An attack directed at the enemy king with the concrete objective of creating a mating net or forced checkmate.

A coordinated arrangement of threats that restricts the king and leads to forced or nearly forced checkmate.

The phase after the opening and before the endgame, where plans, tactics, pawn structures and king safety normally dominate.

A bishop or knight.

The advance of a smaller pawn group against a larger opposing pawn group, usually to create a weakness rather than to promote a pawn.

A trap, usually arising from the Ruy Lopez, in which queenside pawns advance with tempo until a bishop has no safe retreat.

A file containing no pawns from either side, making it a natural route for rooks and queens.

A position with few central pawn obstructions and many open lines, usually increasing the importance of development, piece activity and calculation.

The initial phase of a chess game, when players normally develop pieces, contest the centre and secure their kings.

A sequence of moves within an opening or variation that has been studied or prepared.

Opening lines and ideas studied before a game. When play leaves preparation, the position must be evaluated independently.

A mating pattern, named after the conclusion of Morphy’s Opera Game, in which a rook mates along an open file while a bishop controls the king’s escape square.

A relationship between kings, usually separated by one square, in which having the move can determine whether one king must yield ground.

A protected square, often occupied by a knight, that cannot be challenged by an enemy pawn.

A passed pawn located far from the main pawn group. It can divert the enemy king and allow play on the opposite wing.

A defending piece responsible for two or more essential duties and therefore unable to meet every threat.

A pawn with no opposing pawn ahead of it on the same or adjacent files, giving it a potential route to promotion.

A pawn move or exchange intended to alter a pawn structure and open lines or create weaknesses.

A greater number of pawns than the opponent on one part of the board, which may be used to create a passed pawn.

The strategic or tactical use of pawn advances, exchanges and breaks to change the structure, gain space or create passed pawns.

The arrangement of the pawns, which strongly influences plans, weak squares, open lines and piece placement.

A fundamental defensive rook-and-pawn versus rook position in which the defending rook holds the third rank from its own side, or sixth rank from the attacker’s side, before checking from behind.

An attack by a bishop, rook or queen that restricts an intervening piece because moving it would expose the king, a more valuable piece or a critical square.

A pawn that appears safe to capture but whose capture permits a tactical or positional punishment.

The complete arrangement of the pieces and pawns at a particular moment, together with the side to move and relevant rights.

Decision-making that accounts for the position, the clock, the opponent’s resources and the difficulty of finding accurate moves over the board.

A final safety check before moving: visualise the candidate move on the board, then examine the opponent’s strongest checks, captures and threats in the resulting position.

Developing the queen too early when it can be attacked by useful developing moves, allowing the opponent to gain tempi.

The strategic method of creating or attacking a second weakness when the defender can adequately protect the first.

The compulsory replacement of a pawn that reaches the farthest rank by a queen, rook, bishop or knight of the same colour.

Anticipating the opponent’s intended plan or threat and preventing or reducing it before pursuing one’s own plan.

A passed pawn defended by another pawn.

An opening beginning 1.d4 d5 2.c4, in which White challenges Black’s central d-pawn.

A move that is not a check or capture but creates, prevents or strengthens an important idea.

One of the board’s eight horizontal rows, numbered 1 to 8.

A time control in which each player has more than ten but less than sixty minutes for the entire game, including any increment calculation under FIDE rules.

A numerical estimate of playing strength based on competitive results within a particular rating system.

A pin in which moving the pinned piece is legal but normally exposes a more valuable piece or causes another serious disadvantage.

A tactic that captures, exchanges or drives away a piece that protects an important square or target.

A selected and studied set of openings and variations that a player intends to use with White and Black.

An endgame in which both sides retain at least one rook. Rook activity, checking distance, passed pawns and king activity are normally critical.

An active rook placed on the opponent’s second rank—White’s seventh or Black’s second—where it may attack pawns laterally and restrict the king.

A visual method for deciding whether a king can catch an unsupported passed pawn without calculating every move.

An opening beginning 1.e4 e5 2.Nf3 Nc6 3.Bb5, in which White develops while applying pressure to the knight defending e5.

Standard Algebraic Notation: the concise notation used to record legal chess moves, including captures, checks, mate and necessary disambiguation.

An opening beginning 1.e4 d5, in which Black immediately challenges White’s e-pawn.

An early checkmate threat against f7 or f2, usually created by a queen and bishop. Accurate defence meets the threat while continuing development.

A file containing pawns from only one side. It is semi-open for the player who has no pawn on that file.

A position in which some pawn lines have opened while others remain closed, combining features of open and closed play.

An opening beginning 1.e4 c5, creating an asymmetrical pawn structure and immediate counterplay against the centre.

The deliberate reduction of material or complexity through exchanges, often used to reduce counterplay when ahead.

A practical pin in which a piece can move legally but is tactically restricted because moving would allow mate or another decisive consequence.

A line attack on a valuable piece that must move, exposing a second target behind it.

Checkmate by a knight when the enemy king is completely surrounded by its own pieces and has no escape square.

The amount of board territory a player controls, particularly the useful squares available behind an advanced pawn structure.

A draw that occurs when the player to move is not in check and has no legal move.

Longer-term planning based on persistent features such as pawn structure, king safety, space, weak squares and piece activity.

A feature suggesting that a tactic may exist, such as an exposed king, undefended piece, overloaded defender or aligned targets.

A recurring tactical idea or pattern, such as a fork, pin, skewer, deflection or discovered attack.

Concrete, normally short-term play based on forcing moves and recurring motifs that can win material, give mate or achieve another immediate result.

One unit of time represented by a move. A move made with a threat may gain a tempo by forcing the opponent to respond.

An intended move or sequence that will produce a favourable result unless the opponent responds.

A stage of a game in which a player has very little time remaining and must adjust calculation and decision-making accordingly.

A prepared tactical idea that invites a plausible inaccurate reply and has a verified punishment. A sound move should remain acceptable if the opponent avoids the trap.

A manoeuvre, often by a king, that returns to the same position after three moves but changes whose turn it is.

A piece protected by no friendly piece. It may become a tactical target even when it is not currently attacked. The established coaching expression “loose piece” and mnemonic LPDO refer to this idea.

Promotion of a pawn to a rook, bishop or knight rather than a queen, normally for a specific tactical or stalemate-related reason.

A particular branch of an opening or a calculated sequence considered during analysis.

An opening beginning 1.e4 e5 2.Qh5, also called the Parham Attack, which creates an early threat against f7 but develops the queen prematurely.

A square that cannot be adequately controlled by a pawn and may become a stable entry point or outpost for an enemy piece.

A repeated series of discovered checks and captures, normally involving a rook and bishop, that wins material with tempo.

The piece contributing least to the position. Improving it is a common strategic method when no forcing action is available.

In a bishop-and-rook-pawn ending, a bishop that does not control the pawn’s promotion square. If the defending king reaches that corner, the position is often drawn.

A line-piece attack or defence that operates through an intervening piece, becoming effective when that blocker moves or is removed.

A position in which the obligation to move worsens the player’s position, whereas passing would avoid the concession.

An in-between move, usually a check or strong threat, played before an expected recapture or continuation.