conjugation has 11 distinct synonyms spread across 3 of its 6 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 state of being joined together
the complete set of inflected forms of a verb
a class of verbs having the same inflectional forms
the act of pairing a male and female for reproductive purposes
“the casual couplings of adolescents”
the act of making or becoming a single unit
“the union of opposing factions”
Synonyms, antonyms and the broader and narrower relations for conjugation come from Princeton University’s WordNet. Full sources and licences.