hinge has 1 distinct synonym spread across 1 of its 3 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 joint that holds two parts together so that one can swing relative to the other
a circumstance upon which subsequent events depend
“his absence is the hinge of our plan”
Synonyms, antonyms and the broader and narrower relations for hinge come from Princeton University’s WordNet. Full sources and licences.