Synonym / antonym
A word that has a closely similar meaning to another word. English has very few true synonyms (e.g. sofa / couch / settee), but many near synonyms, e.g. house – dwelling – home – abode – pad. The existence of synonyms allows variety of word choice according to style and register. A list of synonyms is available in a thesaurus.
An antonym is a word with directly ‘opposite’ meaning, e.g. black/white good/bad.