isolation has 1 distinct synonym spread across 1 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.
a state of separation between persons or groups
Synonyms, antonyms and the broader and narrower relations for isolation come from Princeton University’s WordNet. Full sources and licences.
a feeling of being disliked and alone
the act of isolating something; setting something apart from others
(psychiatry) a defense mechanism in which memory of an unacceptable act or impulse is separated from the emotion originally associated with it
a country's withdrawal from international politics
“he opposed a policy of American isolation”