A concept is an abstract idea representing the fundamental characteristics of what it represents. Concepts arise as abstractions or generalisations from experience or the result of a transformation of existing ideas. The concept is instantiated (reified) by all of its actual or potential instances, whether these are things in the real world or other ideas. Concepts are treated in many if not most disciplines both explicitly, such as in linguistics, psychology, philosophy, etc., and implicitly, such as in mathematics, physics, etc. In informal use the word concept often just means any idea, but formally it involves the abstraction component.