heartsease has 15 distinct synonyms spread across 4 of its 4 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.
a common and long cultivated European herb from which most common garden pansies are derived
violet of Pacific coast of North America having white petals tinged with yellow and deep violet
common Old World viola with creamy often violet-tinged flowers
the absence of mental stress or anxiety
Synonyms, antonyms and the broader and narrower relations for heartsease come from Princeton University’s WordNet. Full sources and licences.