affiliation has 3 distinct synonyms spread across 1 of its 2 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 social or business relationship
“a valuable financial affiliation”
the act of becoming formally connected or joined
“welcomed the affiliation of the research center with the university”
Synonyms, antonyms and the broader and narrower relations for affiliation come from Princeton University’s WordNet. Full sources and licences.