In historical linguistics, the wave model or wave theory 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, affecting a gradually expanding cluster of dialects. 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 in some languages. by descent from a proto language.

The wave theory challenges the family tree theory.  The wave theory holds that within the original common language before differentiation, there are dialect differences, and the characteristics of these different dialects will spread to all directions like waves, so that different languages ​​have some of the same characteristics; languages ​​after differentiation  Nor do they develop in a vacuum, and they also affect each other.