division has 11 distinct synonyms spread across 6 of its 12 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.
an army unit large enough to sustain combat
“two infantry divisions were held in reserve”
the act or process of dividing
an administrative unit in government or business
(biology) a group of organisms forming a subdivision of a larger category
(botany) taxonomic unit of plants corresponding to a phylum
a unit of the United States Air Force usually comprising two or more wings
an arithmetic operation that is the inverse of multiplication; the quotient of two numbers is computed
the act of dividing or partitioning; separation by the creation of a boundary that divides or keeps apart
Synonyms, antonyms and the broader and narrower relations for division come from Princeton University’s WordNet. Full sources and licences.