fringe has 5 distinct synonyms spread across 4 of its 8 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 part of the city far removed from the center
“they built a factory on the outskirts of the city”
one of the light or dark bands produced by the interference and diffraction of light
a social group holding marginal or extreme views
“members of the fringe believe we should be armed with guns at all times”
an ornamental border consisting of short lengths of hanging threads or tassels
Synonyms, antonyms and the broader and narrower relations for fringe come from Princeton University’s WordNet. Full sources and licences.