downtown has 1 distinct synonym spread across 1 of its 3 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 uptown.
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 central area or commercial center of a town or city
“the heart of Birmingham's downtown”
of or located in the lower part of a town, or in the business center
“downtown Manhattan”
Synonyms, antonyms and the broader and narrower relations for downtown come from Princeton University’s WordNet. Full sources and licences.
toward or in the lower or central part of town