thing has 2 distinct synonyms spread across 1 of its 12 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.
Synonyms, antonyms and the broader and narrower relations for thing come from Princeton University’s WordNet. Full sources and licences.
a statement regarded as an object
“to say the same thing in other terms”
any attribute or quality considered as having its own existence
“the thing I like about her is ...”
a special objective
“the thing is to stay in bounds”
a persistent illogical feeling of desire or aversion
“he has a thing about seafood”
a separate and self-contained entity