library has 3 distinct synonyms spread across 2 of its 5 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 room where books are kept
“they had brandy in the library”
a collection of literary documents or records kept for reference or borrowing
Synonyms, antonyms and the broader and narrower relations for library come from Princeton University’s WordNet. Full sources and licences.
a depository built to contain books and other materials for reading and study
(computing) a collection of standard programs and subroutines that are stored and available for immediate use
a building that houses a collection of books and other materials