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Chess problem terminology

This is a list of terms used in chess problems. For a list of unorthodox pieces used in chess problems, see fairy chess piece. For a list of terms used in chess is general, see chess terminology.

Actual play - see post-key play.
Albino - a problem in which, at some point in the solution, a white pawn on its starting square makes each of its four possible moves (forward one square, forward two squares, capture to the left, capture to the right). If the same behaviour is exhibited by a black pawn, it is a Pickaninny.
Allumwandlung - a problem in which the solution includes pawn promotions to all possible pieces (in orthodox chess, to bishop, knight, rook and queen; in fairy chess, possibly to fairy pieces).
Anticipated - if the theme and setting of a particular problem has already appeared in an earlier problem without the knowledge of the later composer, the problem is said to be anticipated. The position does not have to be exactly the same, just very similar. Where this is done deliberately by the later composer, the term plagiarised is more appropriate. There is a real chance of anticipation if the problem has a realitvely simply theme, since there are only a finite number of positions and themes, and chess problems have been composed for hundreds of years. However, anticipations are not always noticed immediately.
Aristocrat - a problem which has no pawns in the initial position.
Babson task - a problem in which black promotion defences to all possible pieces are answered by white promotions to the same piece black has promoted to. An extreme form of Allumwandlung.
Block - a problem in which the key provides no threat, but instead puts black in a position of zugzwang, where every move leads to a mate. In a complete block, all of black's moves have mates provided in the set play and the key is simply a waiting move; in an incomplete block, not all black moves are provided with mates in the set play - the key provides for those that don't; in a mutate some of the mates provided in the set play are changed following the key.
By-play - variations not directly connected to the problem's theme.
Clearance - in general, the movement of one piece so that another can move to a particular square. In square vacation the first piece moves so that the second can occupy the square on which it stood; in line vacation the first piece moves so that the second can pass over the square on which is stood on the way to its destination; line clearance, also known as the Bristol, is a particular type of line vacation in which a piece moves along a line so that another piece can move a shorter distance behind it along the same line.
Cook - a second key move, unintended by the composer. A cook is a serious flaw, and invalidates a problem. The publication of cooked problems was once common, but in the modern era computers can be used to check for cooks, and cooked problems are rarely published.
Cylindrical board - a board in which the a and h-files are considered to be connected (a "vertical cylinder") or the first and eighth ranks are connected (a "horizonal cylinder"). A combination of the vertical and horizontal cylinders is called an "anchor ring".
Directmate - a type of problem where white, moving first, is required to checkmate black in a specified number of moves against any defence. Such a problem is usually indicated by the stipulation "mate in two" (or however many moves is necessary) or "checkmate in two". The term directmate is useful to distinguish these sorts of problems from helpmates, selfmates, reflexmates and others.
Dual - ideally, white should have only one move at each juncture which solves a problem - if white has an alternative at any stage other than the first move, this is a dual. A dual is not as serious a flaw as a cook, and in minor lines, duals may be permissible (opinions differ on this point). Some problems make a virtue out of dual avoidance - of two apparently equivalent white moves, only one works.
Duplex - a type of problem in which there are two solutions, the second one reversing the roles of the colours in the first. The most common type is the duplex helpmate, in which the two solutions to be found are: black moves first and cooperates with white to be mated; and white moves first and cooperates with black to be mated.
Economy - economy is generally regarded as a good thing in chess problem composition, though exactly what is meant by it, and exactly what it is most important to be economical with, is open to debate. Eceonomy of material or force (not using more pieces than necessary), economy of space (using the chessboard to its fullest, not cramming all the pieces into one corner) and economy of motivation (keeping all lines in the solution relevent to the theme) are all regarded as important.
Excelsior - a problem in which a pawn on its starting square in the initial position moves the length of the board to be promoted during the course of the solution. Named after one such problem by Sam Loyd.
Fairy chess - chess played with non-orthodox rules. Examples are circe, maximummers, problems with unorthodox pieces (fairy pieces) and problems with unorthodox boards (such as cylindrical boards, or grid boards).
Flight (square) - a sqaure to which the black king can legally move (that is, one not guarded by a white piece, and not occupied by a black piece). If black plays a piece to one of these squares, thus decreasing the king's mobility, it is a self-block. If he moves a piece from one of these squares, it is square-vacation.
Grid-board - a kind of board used in fairy chess which is divided into a grid of 16 2x2 squares. For a move to be legal, the moving piece must pass over at least one of these grid-lines.
Grimshaw - a common device featuring two black pieces mutually interfering with each other on a single square.
Heavy - adjective applied to a problem which has a relatively large number of pieces in the initial position. Heaviness should be avoided where possible in the interests of economy.
Helpmate - a type of problem where white and black cooperate to put black in mate within a specified number of moves. Unless otherwise specified, black moves first in helpmates. See also duplex.
Interference - the closure of the line of one piece by a second piece, thus limiting its movement and cutting it off from certain squares. Various names are given to particular types of interference, among them Grimshaw, Novotny, anti-Bristol, Holzhausen, Wurzburg-Plachutta and Plachutta.
Key - the first move of a solution. A problem which unintentionally has more than one key is said to be cooked.
Light - adjective applied to a problem which has a relatively small number of pieces in the initial position. Lightness is usually desireable in the interests of economy.
Maximummer - a problem in which black must make the geometrically longest moves available to him, as measured from square-centre to square-centre. If two or more longest moves of equal length are available, black may choose between them. This stipulation is most often attached to selfmates.
Meredith - a problem with no less than eight and no more than twelve pieces on the board in the starting postion. A problem with less than eight pieces is a miniature.
Miniature - a problem with no more than seven pieces on the board in the initial position.
More-mover - a directmate with the stipulation "white to move and checkmate black in no more than n moves against any defence" where n is greater than 3. In composition tourneys, there are often separate classes for more-movers, two-movers and three-movers (as well as classes for helpmates, selfmates and others).
Mutate - a type of block problem in which at least one mate in the set play is changed following the key.
Novotny - a sacrificed white piece can be taken by two differently-moving black pieces--whichever piece makes the capture, it interferes with the other. Essentially a Grimshaw brought about by a white sacrifice on the critical square.
Phase (of play) - play after the key, after tries and set play each constitutes a phase of play. A problem with set play is said to have two phases (the set play being one phase, the post-key play being another); a problem with three tries would be a four phase problem (each try being one phase, with the post-key play the fourth).
Pickaninny[?] - a problem in which, at some point in the solution, a black pawn on its starting square makes each of it's four possible moves (forward one square, forward two squares, capture to the left and capture to the right). If the same behaviour is exhibited by a white pawn, it is an albino.
Plachutta - a sacrificed white piece can be taken by two similarly-moving black pieces--whichever piece makes the capture, it interferes with the other. Essentially a pair of Holzhausen[?] interferences (or a Warzburg-Plachutta[?] interference) brought about by a white sacrifice on the critical square.
Post-key play - the play following the key, that is, the lines of play which fulfill the stipulation of the problem. This is opposed to set play and virtual play (both of which may also be important elements in the attractiveness of a problem).
Proof game - a type of problem in which the job of the solver is to construct a game of a given number of moves in which the final position is the one given by the composer. A kind of retrograde analysis.
Reflexmate - a selfmate in which both sides must deliver checkmate if they are able to do when it is their move. A problem where this stipulation applies only to black is a semi-reflexmate.
Retrograde analysis, retroanalysis - deduction of the move or moves leading up to a given position. A problem may be completely made up of retrograde analysis (as in a proof game, or a problem in which the task is to determine black's last move, for example), or it may be a part of some larger problem (for example, it may be necessary to determine that black has moved his king leading up to a given position, meaning he is unable to castle, and thus rendering correct a solution which would be otherwise incorrect).
S - in algebraic notation, the letter N is usually used to indicate the knight. In chess problems, however, the letter S (standing for Springer, the German name for the knight) is often used instead, with N instead being reserved for the popular fairy piece, the nightrider.
Selfmate - a type of problem where white forces black to mate him against black's will within a specified number of moves.
Series-mover - a problem in which one side makes a series of moves without reply.
Set play - play which would be possible from the initial position of a problem if it was the other player to move first. For example, in a directmate, set play consists of lines of play starting with a black move (rather than a white move). When set play exists, the key move may be something which does not change the set play lines, in which case the problem is a complete block, or the lines in the set play may change, in which case the problem is a mutate. Set play is one phase of play.
Theme: the underlying idea of a problem, which gives it logic, coherence and beauty.
Threat - a move or variation which white will play (usually following his key) if black does nothing to defend against it. Problems which do not have threats following the key are blocks.
Three-mover - a problem with the stipulation "white to move and checkmate black in no more than three moves against any defence". In composition tourneys, there are often separate classes for three-movers, two-movers and more-movers (as well as classes for helpmates, selfmates and others).
Try - a move which almost solves a problem, but is defeated by a single black defence, as opposed to the key (which actually does solve the problem). Variations after tries are called virtual play and may be an important part of what makes some problems pleasing.
Twin - two or more problems which are slight variations on each other, composed by the same person. The variation is usually brought about by adding, removing or moving a piece in the initial setup.
Two-mover - a problem with the stipulation "white to move and checkmate black in two moves against any defence". In composition tourneys, there are often separate classes for two-movers, three-movers and more-movers (as well as classes for helpmates, selfmates and others).
Version - said of a problem which is an adaptation of an earlier one (it may have been altered to improve its economy or to eliminate a cook).
Virtual play - the play following a try, as opposed to set play and post-key play.

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