Chess analysis terms, explained
What every label in a chess game report actually means — from Brilliancy to Blunder, plus centipawns, accuracy and ECO codes. These are the exact definitions Lumichess uses when it grades your games, not general ones.
Brilliancy
A move that gives up material for a concrete, engine-verified gain — typically a sacrifice the engine agrees with. It is the rarest label in a Lumichess report: the move must be both the best available and materially counter-intuitive. Most games contain none.
Great move
The only move that holds the position together, or one that seizes an advantage the alternatives miss. Unlike a Brilliancy it does not require a sacrifice, but it does require that the second-best move be meaningfully worse.
Best move
The move the engine itself would play in that position. Nothing was lost, and no better continuation existed at the search depth used.
Book move
A move that appears in established opening theory. Lumichess marks these as Book rather than grading them, because playing known theory is not the same as finding a move over the board. The first move that is not Book is the point you left preparation.
Inaccuracy
A move that measurably worsens your position without losing it. In practice this is the slow-drift category: nothing is hanging, but the pressure quietly reverses.
Mistake
A move that hands over a significant part of your advantage, or lets your opponent back into a game you were controlling.
Miss
You had a winning continuation available and played something else. The label exists separately from Mistake because failing to convert an opportunity and actively worsening your position are different habits with different fixes.
Blunder
A move that loses material or the game outright. In a Lumichess report the largest single swing in the game is called out directly, along with the move you should have played instead.
Centipawn
One hundredth of a pawn, the unit engines use to score a position. An evaluation of +150 centipawns means White stands about a pawn and a half better. Lumichess uses centipawns internally but does not grade your moves on them directly — see accuracy below for why.
Accuracy
A percentage describing how closely you played to the engine across a whole game. Lumichess converts each evaluation into a win probability first, then scores how much of that probability your move gave away. This matters because losing 300 centipawns in a sharp middlegame and losing 300 in a position you were winning by a rook are not the same error, though a raw centipawn average treats them identically.
Evaluation graph
The line drawn across the whole game showing which side stood better at every point. It is usually the fastest way to find the move a game turned on: look for the cliff, not the numbers.
ECO code
Encyclopaedia of Chess Openings classification — a letter A to E plus two digits identifying an opening family, such as B20 for the Sicilian Defense. Browse every family in our chess openings index.