additive has 1 distinct synonym spread across 1 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. Its one recorded opposite is subtractive.
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.
designating or involving an equation whose terms are of the first degree
characterized or produced by addition
“an additive process”
something added to enhance food or gasoline or paint or medicine
Synonyms, antonyms and the broader and narrower relations for additive come from Princeton University’s WordNet. Full sources and licences.