sun has 9 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.
the star that is the source of light and heat for the planets in the solar system
“the sun contains 99.85% of the mass in the solar system”
a person considered as a source of warmth or energy or glory etc
any star around which a planetary system revolves
first day of the week; observed as a day of rest and worship by most Christians
Synonyms, antonyms and the broader and narrower relations for sun come from Princeton University’s WordNet. Full sources and licences.