1. not formal

- conservative people unaccustomed to informal dress

- an informal free-and-easy manner

- an informal gathering of friends

Similar word(s): casual, daily, everyday, relaxed, folksy, unceremonial, unceremonious, informal

2. not officially recognized or controlled

- an informal agreement

Similar word(s): unofficial, loose

3. used of spoken and written language

Similar word(s): informal, colloquial, conversational, common, vernacular, vulgar, epistolary, epistolatory, slangy, subliterary, nonliterary, unliterary, unrhetorical

4. having or fostering a warm or friendly and informal atmosphere

- a relaxed informal manner

Similar word(s): friendly, cozy, intimate

Sentences with informal as an adjective:

- an informal get-together

- informal clothes