A colloquialism is a word, phrase, or other form used in language. Dictionaries often display colloquial words and phrases with the abbreviation colloq. as an identifier.Colloquial language, colloquial dialect, or informal language is a variety of language commonly employed in conversation or other communication in informal situations. Colloquial refers to the language or linguistic usage made in a particular region or location. Colloquial form of a language is understood only in a particular region or location where it is spoken. The word colloquial by its etymology originally referred to speech as distinguished from writing, but colloquial register is fundamentally about the degree of informality or casualness rather than the medium, and some usage commentators thus prefer the term casualism.
Colloquial language is distinct from formal speech or formal writing. It is the variety of language that speakers typically use when they are relaxed and not especially self-conscious.
Some colloquial speech contains a great deal of slang, but some contains no slang at all. Slang is permitted in colloquial language, but it is not a necessary element. Other examples of colloquial usage in English include contractions or profanity.
In the philosophy of language, the term "colloquial language" refers to ordinary natural language, as distinct from specialized forms used in logic or other areas of philosophy. In the field of logical atomism, meaning is evaluated in a different way than with more formal propositions.