Transposition (chess)

In chess, a transposition is a sequence of moves that results in a position which may also be reached by another, more common sequence of moves. Transpositions are particularly common in the opening, where a given position may be reached by different sequences of moves. Players sometimes use transpositions deliberately, to avoid variations they dislike, lure opponents into unfamiliar or uncomfortable territory or simply to worry opponents.
In chess the verb "transpose" means to shift the game onto a different opening track from which it started.
Transposition tables are an essential part of a computer chess program.
Transpositions exist in other abstract strategy games such as shogi, go, tic-tac-toe and hex.
Examples.
Positions reached by different routes.
For instance, the first position can be obtained from the Queen's Gambit:
But this position can also be reached from the English Opening:
so the English Opening has transposed into the Queen's Gambit.
The second position shows another example. The position can arise from the French Defence:
The identical position can also be reached, with two extra moves played by each side, from the Petrov Defense:
The third position shows another example. The position can arise from the Sveshnikov variation of the Sicilian Defence:
The identical position can also be reached, with one extra move played by each side, from the Four Knights variation of the Sicilian Defence:
The position on the right, featuring a Maróczy Bind, can be reached from the Sicilian Defence:
The identical position can also be reached from the King's Indian Defence:
The position on the right can be reached from the Sicilian Defence:
The identical position can also be reached from the Pirc Defence:
The position on the right, featuring an "isolani" can be reached by many different openings and move orders. For example, there's the Nimzo-Indian Defence:
Caro–Kann Defence:
Transposition possibilities of some openings.
Some openings are noted for their wide range of possible transpositions, for example the Catalan Opening and Sicilian Defence.
For a simple example, the opening moves 1.d4 e6 can transpose very quickly into a wide range of openings, including: