Triangulation in chess is an endgame related tactic to put the opponent in zugzwang by explicitly losing a tempo. Triangulation performs an artificial null move, a piece (except pawn and knight) uses three moves to return to its original square, while the defending side is not able to do so.
Most often triangulation occurs with the king in pawn endings to "win" the opposition. Queen-triangulation is a theme in KQKR, as demonstrated in Philidor's KQKR position , while rook-triangulation  is a motive in rook endgames, and bishop-triangulation happens rarely in bishop versus knight endings . In blocked pawn endgames, triangulation and opposition is incorporated in the general concept of corresponding squares.
Triangulation, like any other zugzwang related motives, requires some care in search using null move pruning. Most programs either disable null move pruning completely in such late endgames, or at least perform a verification search.
- Triangulation (chess) from Wikipedia
- Triangulation (disambiguation) from Wikipedia
- Chess Training: Corresponding Squares and Triangulation