immutable has 1 distinct synonym spread across 1 of its 2 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. Its one recorded opposite is mutable.
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.
not subject or susceptible to change or variation in form or quality or nature
“the view of that time was that all species were immutable, created by God”
1 of the 2 recorded senses carries no synonym, antonym or related term, so it is not shown above. Every sense, with its definition and examples, is on the full entry for immutable.
Synonyms, antonyms and the broader and narrower relations for immutable come from Princeton University’s WordNet. Full sources and licences.