Zugzwang
Also called Compulsion to move.
Any move makes your position worse, but you must move.
Usually having the move is an advantage. In zugzwang it is a burden: every legal move gives something away. It is rare in the middlegame and common in endgames, especially king and pawn endings.
It is not stalemate: in zugzwang there are legal moves, they are just all bad. Opposition and triangulation are ways to put the other side in zugzwang.
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