informal

UK: /ɪnˈfɔː^rm^əl/ US: /ɪnˈfɔrməl/ ,(in fôr′məl)

WordReference Random House Learner's Dictionary of American English © 2025

in•for•mal /ɪnˈfɔrməl/   adj. 

1. without formality;
   casual:
   an informal visit.
2. not according to the official manner:
   informal proceedings.
3. Linguistics suitable to or characteristic of casual speech or writing:
   an informal use of a word.

in•for•mal•ly, adv.: 

dressed informally for the party.

See -form-.
Synonyms

See colloquial.

WordReference Random House Unabridged Dictionary of American English © 2025

in•for•mal  (in fôr′məl), adj. 

1. without formality or ceremony;
   casual:
   an informal visit.
2. not according to the prescribed, official, or customary way or manner;
   irregular;
   unofficial:
   informal proceedings.
3. Informal Terms, Linguistics suitable to or characteristic of casual and familiar, but educated, speech or writing.
4. Grammar characterizing the second singular pronominal or verbal form, or its use, in certain languages:
   the informal
   tu in French.

• in-³ + formal¹ 1595–1605

in•for′mal•ly, adv. 
Synonyms

• 1. natural, easy.
• 2. unconventional.
• 3. See colloquial. 

Antonyms

• 2. conventional.

Collins Concise English Dictionary © HarperCollins Publishers::

informal / ɪnˈfɔːməl/ adjective

1. not of a formal, official, or stiffly conventional nature
2. appropriate to everyday life or use
3. denoting or characterized by idiom, vocabulary, etc, appropriate to everyday conversational language rather than to formal written language
4. denoting a second-person pronoun in some languages used when the addressee is regarded as a friend or social inferior

inˈformally adverb