Synchrony and diachrony are two complementary viewpoints in linguistic analysis. A synchronic approach (from συν- "together" and χρόνος "time") considers a language at a moment in time without taking its history into account. Synchronic linguistics aims at describing a language at a specific point of time, often the present. 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. For example, the study of Middle English—when the subject is temporally limited to a sufficiently homogenous form—is synchronic focusing on understanding how a given stage in the history of English functions as a whole. The diachronic approach, by contrast, studies language change by comparing the different stages. The terms synchrony and diachrony are often associated with historical linguist Ferdinand de Saussure, who considered the synchronic perspective as systematic but argued that language change is too unpredictable to be considered a system. The concepts were theorized by the Swiss linguist Ferdinand de Saussure, professor of general linguistics in Geneva from 1896 to 1911, and appeared in writing in his posthumous Course in General Linguistics published in 1916. Saussure's teachers in historical-comparative and reconstructive linguistics such as Georg Curtius advocated the neo-grammarian manifesto according to which linguistic change is based on absolute laws. Thus, it was argued that ancient languages without surviving data could be reconstructed limitlessly after the discovery of such laws. In contradiction to his predecessors, Saussure demonstrated with multiple examples in his Course that such alleged laws are too unreliable to allow reconstructions far beyond the empirical data. Therefore, in Saussure's view, language change (diachrony) does not form a system. By contrast, each synchronic stage is held together by a systemic equilibrium based on the interconnectedness of meaning and form.
Frédéric Kaplan, Maud Ehrmann, Sofia Ares Oliveira, Raphaël Barman