breakdown has 8 distinct synonyms spread across 5 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 act of disrupting an established order so it fails to continue
“the social dislocations resulting from government policies”
(biology) the process of decay caused by bacterial or fungal action
an analysis into mutually exclusive categories
Synonyms, antonyms and the broader and narrower relations for breakdown come from Princeton University’s WordNet. Full sources and licences.