unite has 7 distinct synonyms spread across 6 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. Its one recorded opposite is divide.
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.
act in concert or unite in a common purpose or belief
become one
“Germany unified officially in 1990”
Synonyms, antonyms and the broader and narrower relations for unite come from Princeton University’s WordNet. Full sources and licences.