Zugzwang annotation symbol

⊙ or ⨀ marks zugzwang. This is a position in which the player to move must make a legal move, but every option worsens that player's situation. If passing and leaving the position unchanged were allowed, the player would prefer to do so; chess rules do not permit a pass.

The NAG table uses different codes for White being in zugzwang and Black being in zugzwang, even though both may display the same ⊙ glyph. NAG means Numeric Annotation Glyph, a numeric annotation code. The number or surrounding context, rather than the visible shape alone, identifies the affected side.

Zugzwang is neither stalemate nor checkmate. In stalemate, the player is not in check but has no legal move, so the game is drawn. In checkmate, the king is attacked and no legal reply exists, so the game ends. In zugzwang legal moves do exist, but every one concedes something important, such as a square, a pawn, or a favorable king position.