Speech has both an individual and a social side, and we cannot conceive of one without the other. - Ferdinand de Saussure

Language can be compared to a sheet of paper: thought is its recto and sound its verso: one cannot cut the verso without simultaneously cutting the recto. Similarly, in the matter of language, one can separate neither sound from thought nor thought from sound; such separation could be achieved only by abstraction, which would lead either to pure psychology, or to pure phonology.

Thus we may found the science for the study of the life of signs against the background of social life; it would form part of social psychology, and consequently of general psychology; we shall call it semiology (from Greek sēmeion — 'sign'). That science would explain to us in what signs consist of and by what laws they are governed. Since it is a science which does not yet exist, we do not know what it will be like; it has, however, a reason for its existence, its place is allocated in advance. Linguistics is only a part of that general science ; the laws which semiology will discover, will be applicable also to linguistics, which in turn will be linked with a domain clearly defined throughout the entirety of human affairs.

The linguistic entity is not accurately defined until it is delimited, i.e. separated from everything that surrounds it on the phonic chain. These delimited entities or units stand in opposition to each other in the mechanism of language.