(1) A term used in historical linguistics and sociolinguistics as part of a dynamic model of language change: wave theory suggests that speech variations spread from a specific linguistic area, having maximum effect on adjacent languages, and progressively less effect on languages further away - in much the same way that waves in water radiate from a central point of contact.

(2) A term used in tagmemic grammar as one mode of the analysis of linguistic units: in the wave mode, units at any level are analysed in terms of their status as variants manifested in different contexts, e.g. morphemic or transformational processes. This mode is contrasted with the analysis of units in terms of particles and fields.