unit has 4 distinct synonyms spread across 4 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.
any division of quantity accepted as a standard of measurement or exchange
“the dollar is the United States unit of currency”
an individual or group or structure or other entity regarded as a structural or functional constituent of a whole
“the reduced the number of units and installations”
an organization regarded as part of a larger social group
“the coach said the offensive unit did a good job”
an assemblage of parts that is regarded as a single entity
“how big is that part compared to the whole?”
Synonyms, antonyms and the broader and narrower relations for unit come from Princeton University’s WordNet. Full sources and licences.