seth has 1 distinct synonym spread across 1 of its 2 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.
(Old Testament) third son of Adam and Eve; given by God in place of the murdered Abel
evil Egyptian god with the head of a beast that has high square ears and a long snout; brother and murderer of Osiris
Synonyms, antonyms and the broader and narrower relations for seth come from Princeton University’s WordNet. Full sources and licences.