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Two notations differing by one character, describing mirror-image moves.
Count the letters. Two means the king's side, three means the queen's — and the longer notation matches the longer journey the rook makes. Both are written with the letter O in the Laws, though the digit zero is common in print.
Count the letters: two for the king's side, three for the queen's. The moves send the king in opposite directions.
| Kingside castling (O-O) | Queenside castling (O-O-O) | |
|---|---|---|
| Notation | O-O | O-O-O |
| Which way the king goes | Towards the h-file | Towards the a-file |
| Rook involved | The one nearer the king | The one further from the king |
| Also called | Short castling | Long castling |
| King's final position | Closer to the corner | Further from the corner |
| Relationship (from Symbolwise's records) | Commonly confused with Queenside castling (O-O-O) — Count the letters: two for the king's side, three for the queen's. The moves send the king in opposite directions. | Commonly confused with Kingside castling (O-O) — Three letters for the queen's side, two for the king's. The longer notation matches the longer rook journey. |
FIDE Laws of Chess, Appendix C: Algebraic Notation
Fédération Internationale des Échecs (FIDE) · retrieved 2026-08-02
The governing body's own handbook. Authoritative for the notation FIDE requires in competition — the piece letters, the capture and check marks, castling — and for nothing outside it. Annotation symbols expressing an opinion about a move are deliberately absent from the Laws and are not cited here.
Wikipedia · retrieved 2026-08-02
Tertiary reference. Cited for how a mark is written and read in ordinary practice, and for conventions no governing body issues. Never cited for a claim that a rule says something — the rulebooks below carry those.
Both arms sweeping forward means play continues and no kick is coming. One arm straight up means a kick is coming and cannot score directly. Confusing them changes whether players expect a stoppage.
The plain black flag excludes the competitor: their race is over. The black flag with an orange disc reports a mechanical problem that endangers others and sends the driver to the pits to have it fixed, after which they may rejoin. Both are shown with a number board, both are black, and confusing them costs a competitor a race they could have finished.
A cross means all ten pins fell to the first ball; a forward slash means it took two. The cross carries two deliveries of bonus and the slash only one, which is why three strikes are needed for a frame to reach thirty.
The exclamation mark praises a move, the question mark criticises it. Neither is defined by FIDE: unlike the rest of chess notation these are publishing convention, and two annotators may disagree about the same move.