domain has 11 distinct synonyms spread across 5 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.
(mathematics) the set of values of the independent variable for which a function is defined
people in general; especially a distinctive group of people with some shared interest
“the Western world”
the content of a particular field of knowledge
Synonyms, antonyms and the broader and narrower relations for domain come from Princeton University’s WordNet. Full sources and licences.