Wave model

This article is about the concept of wave in historical linguistics. For other uses, see Wave model (disambiguation).

Diagram based on the wave model originally presented by Johannes Schmidt. The background represents a dialect continuum in its geographical extension. In this Euler diagram, the circles are to be regarded as diachronic: they start from a center and increase in diameter over time, like the concentric waves on a water surface struck by a stone. These circles are (bundles of) characters that were innovated originally across a small portion of the continuum, and later spread out along the social network, moving away from the center. Languages are impermanent sets of speech habits that result from the intersections of the circles. The most conservative language is represented by the area not covered by the circles.

In historical linguistics, the wave model, or wave theory (German: Wellentheorie), is a model of language change in which a new language feature (innovation) or a new combination of language features spreads from its region of origin, being adopted by a gradually expanding cluster of dialects. Each innovation starts at a certain place, and spreads from speaker to speaker, from dialect to dialect, in the same fashion as waves on the water.

The theory was intended as a substitute for the tree model, which did not seem to be able to explain the existence of some features, especially in the Germanic languages, by descent from a proto-language. At its most ambitious, it is a wholesale replacement for the tree model of languages. During the 20th century, the wave model had little acceptance as a model for language change overall, except for certain cases, such as the study of dialect continua and areal phenomena; it has recently gained more popularity among historical linguists, due to the shortcomings of the tree model.