Compensatory lengthening

Compensatory lengthening is a common phonological process whereby the loss of some phonetic material is compensated for by the lengthening of some neighbouring phonetic material.

Greek provides a clear-cut example for the process: Proto-Greek esmi `I am' changes into Attic eimi [eːmi] and Lesbian emmi. That is, the loss of the s is made up for by lengthening the preceding vowel in Attic and the following consonant in Lesbian.

A less obvious case of compensatory lengthening is exemplified by Old Hungarian utu to Modern Hungarian út [uːt] (i.e. [uut]) `road', where the loss of the final vowel causes the lengthening of the preceding vowel. (This process could also be classified as metathesis.)

The frequent occurrence of compensatory lengthening across languages is a strong argument for the separation of the melodic and the temporal aspects of speech, that is, for the autosegmental model of phonological representations.