characteristic has 2 distinct synonyms spread across 2 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. Its one recorded opposite is uncharacteristic.
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.
Synonyms, antonyms and the broader and narrower relations for characteristic come from Princeton University’s WordNet. Full sources and licences.
a distinguishing quality
the integer part (positive or negative) of the representation of a logarithm; in the expression log 643 = 2.808 the characteristic is 2
any measurable property of a device measured under closely specified conditions
typical or distinctive
“heard my friend's characteristic laugh”