intervene has 3 distinct synonyms 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.
be placed or located between other things or extend between spaces and events
“This interludes intervenes between the two movements”
occur between other event or between certain points of time
“the war intervened between the birth of her two children”
Synonyms, antonyms and the broader and narrower relations for intervene come from Princeton University’s WordNet. Full sources and licences.