informal

The word “informal” means relaxed and casual rather than official or ceremonious. In plain terms, casual rather than official or by-the-book.

“Informal” is pronounced ihn-FAW-ml (/ɪnˈfɔɹ.m(ə)l/ in IPA).

Here is “informal” used in a sentence: “It was an informal gathering, just close friends and family.”

Words with a similar meaning to “informal” include not formal, ceremonious, not in accord with the usual regulations and suited for everyday use.

The opposite of “informal” — its antonyms — is formal.

“Informal” is an adjective.

“Informal” is a fairly common word in modern English, usually learned at around the B2 level.

Both describe a relaxed, unofficial style and overlap heavily. Casual tends to emphasize an easygoing, low-effort manner or dress, while informal more broadly means not bound by official rules or ceremony, and is common when describing language, meetings, and writing.

Informal language is relaxed and conversational, using contractions, slang, and simple sentences, as in everyday speech and texts. Formal language avoids these, favoring precise vocabulary and complete structures, and suits official, academic, or professional settings.

Use informal writing for personal messages, texts, casual emails, and friendly contexts where a relaxed tone suits the reader. Choose formal writing for official documents, academic work, and situations that call for professionalism and distance.

Informal describes a relaxed, casual manner or tone, while unofficial means not authorized or not part of the official record. A meeting can be informal yet still official, or official in tone yet unofficial in status.