1. characteristic of or appropriate to ordinary or familiar conversation rather than formal speech or writing; informal.
2. involving or using conversation.
1, 2. Colloquial, conversational, informal refer to types of speech or to usages not on a formal level. Colloquial is often mistakenly used with a connotation of disapproval, as if it meant “vulgar” or “bad” or “incorrect” usage, whereas it is merely a familiar style used in speaking and writing. Conversational refers to a style used in the oral exchange of ideas, opinions, etc.: an easy conversational style. Informal means without formality, without strict attention to set forms, unceremonious: an informal manner of speaking; it describes the ordinary, everyday language of cultivated speakers.
Origin: 1745–55; colloquy + -al
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