The term fashionable refers to behavior adopted generally and uniformly by groups of people in a certain period of time and in a particular field of action. Such behavior is characterized by its broad diffusion within the group, which is also explicitly aware of its transitory nature: what is in fashion is bound soon to go out of fashion. Fashion concerns not only the clothing of the body but also the consumption of objects (e.g., furniture) and ideas. The term is used to denote behaviors and preferences in different areas of action, thought, and moral belief, as well as in music, art, leisure, science, religion, or politics.

In the majority of the European languages, the term used to refer to fashion (mode in French, Mode in ...