sentence has 7 distinct synonyms spread across 3 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. 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 string of words satisfying the grammatical rules of a language
“he always spoke in grammatical sentences”
(criminal law) a final judgment of guilty in a criminal case and the punishment that is imposed
“the conviction came as no surprise”
the period of time a prisoner is imprisoned
“he served a prison term of 15 months”
Synonyms, antonyms and the broader and narrower relations for sentence come from Princeton University’s WordNet. Full sources and licences.