cassia has 3 distinct synonyms spread across 2 of its 3 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 of various trees or shrubs of the genus Cassia having pinnately compound leaves and usually yellow flowers followed by long seedpods
some genus Cassia species often classified as members of the genus Senna or genus Chamaecrista
Chinese tree with aromatic bark; yields a less desirable cinnamon than Ceylon cinnamon
Synonyms, antonyms and the broader and narrower relations for cassia come from Princeton University’s WordNet. Full sources and licences.