morphological has 4 distinct synonyms spread across 3 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.
relating to or concerned with the formation of admissible words in a language
pertaining to geological structure
“geomorphological features of the Black Hills”
relating to or concerned with the morphology of plants and animals
“morphological differences”
Synonyms, antonyms and the broader and narrower relations for morphological come from Princeton University’s WordNet. Full sources and licences.