[adj] not formal; "conservative people unaccustomed to informal dress"; "an informal free-and-easy manner"; "an informal gathering of friends"
[adj] used of spoken and written language
[adj] having or fostering a warm or friendly atmosphere; especially through smallness and informality; "had a cozy chat"; "a relaxed informal manner"; "an intimate cocktail lounge"; "the small room was cozy and intimate"
[adj] not officially recognized or controlled; "an informal agreement"; "a loose organization of the local farmers"
casual, colloquial, common, conversational, cozy, epistolary, epistolatory, everyday, folksy, free-and-easy, friendly, intimate, loose, nonliterary, slangy, subliterary, unceremonial, unceremonious, unliterary, unofficial, vernacular, vulgar