- without formality or ceremony; casual: an informal visit.
- not according to the prescribed, official, or customary way or manner; irregular; unofficial: informal proceedings.
- suitable to or characteristic of casual and familiar, but educated, speech or writing.
- characterizing the second singular pronominal or verbal form, or its use, in certain languages: the informal[hasp] tu in French.
- not of a formal, official, or stiffly conventional nature
- appropriate to everyday life or use
- denoting or characterized by idiom, vocabulary, etc, appropriate to everyday conversational language rather than to formal written language
- denoting a second-person pronoun in some languages used when the addressee is regarded as a friend or social inferior
