| casual(adjective, deliberate, manner, nonchalant) | |
| informal(adjective, simple, casual) | |
| relaxed(verb, adjective, wild, stiff) | |
| intimate(adjective, friendly, private, devoted, personal) | |
| nonformal | |
| unceremonious(adjective, informal, polite) | |
| colloquial(adjective, informal, familiar, particular) | |
| sub-par | |
| unconventional(adjective, odd, different) | |
| conversational | |
| subpar | |
| undignified | |
| capricious | |
| chatty | |
| customary | |
| everyday | |
| familiar(adjective, unhappy) | |
| free and easy(expression, adjective, idiom, relaxed) | |
| normal | |
| plain(adjective, vague, basic, unclear, ambiguous) |
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Formal on
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| APA | Smart Define. (2016). formal thesaurus. Retrieved September 24, 2026, from https://smartdefine.org/formal/thesaurus/antonyms |
| Chicago | Smart Define. 2016. "formal thesaurus" https://smartdefine.org/formal/thesaurus/antonyms (accessed September 24, 2026). |
| Harvard | Smart Define 2016, formal thesaurus, Smart Define, viewed 24 September, 2026, <https://smartdefine.org/formal/thesaurus/antonyms>. |
| MLA | Smart Define. "formal thesaurus" 10 March 2016. Web. 24 September 2026. <https://smartdefine.org/formal/thesaurus/antonyms> |