Historical linguistic theory and practice consist of a large number of chronological "layers" that have been accepted in the course of time and have acquired a permanence of their own. These range from neogrammarian conceptualizations of sound change, analogy, and borrowing, to prosodic, lexical, morphological, and syntactic change, and to present-day views on rule change and the effects of language contact. To get a full grasp of the principles of historical linguistics it is therefore nec ...