conjunction has 10 distinct synonyms spread across 5 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 temporal property of two things happening at the same time
“the interval determining the coincidence gate is adjustable”
the state of being joined together
an uninflected function word that serves to conjoin words or phrases or clauses or sentences
the grammatical relation between linguistic units (words or phrases or clauses) that are connected by a conjunction
Synonyms, antonyms and the broader and narrower relations for conjunction come from Princeton University’s WordNet. Full sources and licences.