cleavage has 1 distinct synonym spread across 1 of its 5 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 split or cleft
“there was a cleavage between the liberal and conservative members”
the breaking of a chemical bond in a molecule resulting in smaller molecules
(embryology) the repeated division of a fertilised ovum
Synonyms, antonyms and the broader and narrower relations for cleavage come from Princeton University’s WordNet. Full sources and licences.
the line formed by a groove between two parts (especially the separation between a woman's breasts)