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.
a special situation
“this thing has got to end”
an action
“how could you do such a thing?”
a special abstraction
“a thing of the spirit”
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
Synonyms, antonyms and the broader and narrower relations for thing come from Princeton University’s WordNet. Full sources and licences.