primitive has 5 distinct synonyms spread across 4 of its 7 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 person who belongs to an early stage of civilization
a mathematical expression from which another expression is derived
a word serving as the basis for inflected or derived forms
“`pick' is the primitive from which `picket' is derived”
1 of the 7 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 primitive.
Synonyms, antonyms and the broader and narrower relations for primitive come from Princeton University’s WordNet. Full sources and licences.