Chess Game Review Glossary
Clear definitions of the chess and game-review terms you'll see across the site — each linked to the tool or guide where it's used.
Every term below appears somewhere in a review. Definitions are short and link to the tool or guide where the concept is used. New to reviews? Start with how to read a game review.
Game review
A move-by-move analysis of a finished game that grades each move, scores each player's accuracy, names the opening, and highlights the turning points. Learn more →
Accuracy
How closely a player's moves matched the engine's best, expressed 0–100%. It is computed from the win probability lost on each move using lichess's open accuracy formula. Learn more →
Average centipawn loss (ACPL)
The average evaluation, in centipawns, that a player gave up per move versus the engine's best. Lower is better; strong games are often under ~20. Learn more →
Centipawn (cp)
One hundredth of a pawn — the engine's unit of advantage. +100 cp means roughly a one-pawn edge for White. Learn more →
Evaluation (eval)
The engine's score for a position from White's point of view: a positive number favours White, negative favours Black, and a value like “M3” means forced mate in three. Learn more →
Win probability (win%)
The evaluation converted to a 0–100% chance of winning. Move classifications are based on how much win% a move gives up, not raw centipawns — so an error in an already-decided position is judged differently. Learn more →
Brilliant (!!)
A strong move that sacrifices material yet keeps or increases the advantage — a sound sacrifice the engine endorses. Learn more →
Great move
The single good move in a sharp position, where the alternatives would have thrown away much of the advantage. Learn more →
Best move
The engine's top choice in the position. Learn more →
Book move
A known opening-theory move, named from a lichess-derived opening book. Learn more →
Inaccuracy (?!)
A slightly imprecise move that gives up a small slice of your advantage. Learn more →
Mistake (?)
A clear error that meaningfully worsens your position. Learn more →
Blunder (??)
A serious error that loses material or allows a mate — the most costly class of move. Learn more →
Miss
Failing to punish the opponent's error, or letting a forced mate slip away. Learn more →
PGN
Portable Game Notation — the standard plain-text format that records a chess game's moves and tags. It's what you paste in to review a game. Learn more →
FEN
Forsyth–Edwards Notation — a one-line text snapshot of a single position, including whose move it is and castling rights. Learn more →
ECO code
Encyclopaedia of Chess Openings code — a letter-and-number label (A00–E99) that categorises an opening. Learn more →
Opening
The first phase of the game. The review names it from an opening book and marks the moves that are still “in book”. Learn more →
Key moment
A turning point — a brilliancy, a blunder, or the moment theory ended — that the guided review stops at to explain. Learn more →
Estimated rating
A heuristic strength estimate derived from a player's accuracy in a game. It's an approximation for context, not an official rating. Learn more →
Stockfish
The open-source chess engine that powers the analysis here — Stockfish 18, compiled to WebAssembly and run in your browser. Learn more →