Mistake
A mistake is a game review label for a move that clearly worsens a position, costing a meaningful share of the advantage, though it is less severe than a blunder that throws the game away.
Also called: mistake mark
Between an inaccuracy and a blunder sits the mistake: a move that noticeably damages your position without necessarily losing at once. Typical examples include dropping a pawn, allowing a strong outpost, walking into a pin, or misjudging an exchange so that the opponent gains the better structure. Where tools draw the lines between the grades differs, so the same move may be named differently by two programs. For a club player, mistakes are where the learning is. They usually have a concrete cause, such as a missed threat, a miscounted capture sequence or an impatient plan, and the cause can be named. The common error is to note the mark and move on without asking why it happened. A useful habit is to take each marked move and write one sentence about what you were thinking and what you missed. After a handful of games the sentences repeat, and the repeats tell you what to practice. Fix the thinking process behind the move, not only the move itself.
It sits close to Missed win. A missed win is a game review label for a move that fails to take a clearly winning continuation, so a decisive advantage shrinks to something much smaller or disappears entirely.
Computer terms such as "Mistake" are most useful next to a coach who reads your games with you, which is how a first lesson with George Li works.
Related terms
An inaccuracy is the mildest error label in game review, given to a move that is playable but gives up a small amount of advantage compared with the engine's better alternative.
A blunder is a very serious error, such as leaving a piece undefended or missing a decisive tactic, that swings the evaluation so far that a good position turns bad or a bad one becomes lost.
A missed win is a game review label for a move that fails to take a clearly winning continuation, so a decisive advantage shrinks to something much smaller or disappears entirely.
A game review is an automatic engine pass over a finished game that marks each move, shows how the evaluation changed and points out the turning points, mistakes and missed chances.
Post-game analysis is the discussion or private review held right after a game, in which both players or one player alone retrace the moves and identify the turning points, missed ideas and lessons.
Guides that go further
What to decide first, the questions to ask, what a first lesson should show and the red flags to avoid.
How much does chess coaching cost?
Published rates for private, group and subscription chess coaching, with the source and the date of each.
A game review, a read on your level and a written study plan from George Li.
Want to spot this in your own games?
A first lesson starts with your games: George reviews them and builds a study plan around what he finds.