History and change form the two key notions on which diachronic linguistics, the scientific study of language through time, rests. Students of linguistics usually first encounter the concept of diachrony in the context of the famous Saussurean dichotomies, but upon entering more deeply into the matter soon realise that, in practice, synchronic and diachronic perspectives are by no means mutually exclusive: the dynamics of language change can only be grasped by a careful diagnosis of the state of the language at different points in time.