relative has 6 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. Its one recorded opposite is absolute.
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.
an animal or plant that bears a relationship to another (as related by common descent or by membership in the same genus)
estimated by comparison; not absolute or complete
“a relative stranger”
properly related in size or degree or other measurable characteristics; usually followed by `to'
“the punishment ought to be proportional to the crime”
Synonyms, antonyms and the broader and narrower relations for relative come from Princeton University’s WordNet. Full sources and licences.