Structuralist linguistics (De Saussure, 1966) operates with a clear distinction between language system (langue) and language use (parole). The language system is the "language itself," the systematization of all distinguishable signs in a language. As a resource used in all instances of language use, the language system is not bound to a particular event and has been researched as a transcendental object with an objective existence.
The language system is a system of elements on two levels: an *expression level* and a *content level*. Signs are then defined as a combination of a *content element* and an *expression element*. The expression is the phonemes of word and the content is the corresponding mental representation. On the expression level, all representations are mutually separated from each other making them distinct units. On the content level, all the contents represented by the representations are likewise distinctively separated from each other. The distinctive differences between the elements on each plane are the main organizational principles of structural linguistics.