expand has 16 distinct synonyms spread across 5 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. Its one recorded opposite is contract.
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.
add details, as to an account or idea; clarify the meaning of and discourse in a learned way, usually in writing
“She elaborated on the main ideas in her dissertation”
Synonyms, antonyms and the broader and narrower relations for expand come from Princeton University’s WordNet. Full sources and licences.