mistake has 7 distinct synonyms spread across 5 of its 5 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a wrong action attributable to bad judgment or ignorance or inattention
“he made a bad mistake”
an understanding of something that is not correct
“he wasn't going to admit his mistake”
part of a statement that is not correct
“the book was full of errors”
Synonyms, antonyms and the broader and narrower relations for mistake come from Princeton University’s WordNet. Full sources and licences.