Nonconcatenative morphology

In traditional Indo-Europeanist usage, these changes are termed ablaut only when they result from vowel gradations in Proto-Indo-European.

[2]: 72 Changes such as foot/feet, on the other hand, which are due to the influence of a since-lost front vowel, are called umlaut or more specifically I-mutation.

Other forms of base modification include lengthening of a vowel, as in Hindi: or change in tone or stress: Consonantal apophony, such as the initial-consonant mutations in Celtic languages, also exists.

In the analysis provided by McCarthy's account of nonconcatenative morphology, the consonantal root is assigned to one tier, and the vowel pattern to another.

In spoken French, this process can be found in a small subset of plurals (although their spellings follow regular plural-marking rules): /ɔs/ "bone" ↔ /o/ "bones" /œf/ "egg" ↔ /ø/ "eggs" Nonconcatenative morphology is extremely well developed in the Semitic languages in which it forms the basis of virtually all higher-level word formation (as with the example given in the diagram).