Colloquialism or colloquial language is the linguistic style used for casual communication. It is the most common functional style of speech, the idiom normally employed in conversation and other informal contexts. Colloquialism is characterized by wide usage of interjections and other expressive devices; it makes use of non-specialist terminology, and has a rapidly changing lexicon. It can also be distinguished by its usage of formulations with incomplete logical and syntactic ordering.
A specific instance of such language is termed a colloquialism. The most common term used in dictionaries to label such an expression is colloquial.