marriage has 8 distinct synonyms spread across 3 of its 4 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 a married couple voluntarily joined for life (or until divorce)
“a long and happy marriage”
two people who are married to each other
“his second marriage was happier than the first”
the act of marrying; the nuptial ceremony
“their marriage was conducted in the chapel”
a close and intimate union
“the marriage of music and dance”
Synonyms, antonyms and the broader and narrower relations for marriage come from Princeton University’s WordNet. Full sources and licences.