purchase 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. 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.
the acquisition of something for payment
“they closed the purchase with a handshake”
something acquired by purchase
Synonyms, antonyms and the broader and narrower relations for purchase come from Princeton University’s WordNet. Full sources and licences.
a means of exerting influence or gaining advantage
“he could get no purchase on the situation”
the mechanical advantage gained by being in a position to use a lever