In contrast, a diachronic (from δια- "through" and χρόνος "time") approach, as in historical linguistics, considers the development and evolution of a language through history.
[1] For example, the study of Middle English—when the subject is temporally limited to a sufficiently homogeneous form—is synchronic focusing on understanding how a given stage in the history of English functions as a whole.
Saussure illustrates the historical development of languages by way of his distinction between the synchronic and the diachronic perspective employing a metaphor of moving pictures.
[5] A dualistic opposition between synchrony and diachrony has been carried over into philosophy and sociology, for instance by Roland Barthes and Jean-Paul Sartre.
[7] In 1970 Eugenio Coșeriu, revisiting De Saussure's synchrony and diachrony distinction in the description of language, coined the terms diatopic, diastratic and diaphasic to describe linguistic variation.