say has 13 distinct synonyms spread across 6 of its 12 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.
speak, pronounce, or utter in a certain way
“She pronounces French words in a funny way”
communicate or express nonverbally
“What does this painting say?”
utter aloud
“She said `Hello' to everyone in the office”
recite or repeat a fixed text
“Say grace”
the chance to speak
“let him have his say”
1 of the 12 recorded senses carries no synonym, antonym or related term, so it is not shown above. Every sense, with its definition and examples, is on the full entry for say.
Synonyms, antonyms and the broader and narrower relations for say come from Princeton University’s WordNet. Full sources and licences.