ABLAUT

In linguistics, the Indo-European ablaut ( AB-lowt, from German Ablaut pronounced [ˈap.laʊt]) is a system of apophony (regular vowel variations) in the Proto-Indo-European language (PIE). An example of ablaut in English is the strong verb sing, sang, sung and its related noun song, a paradigm inherited directly from the Proto-Indo-European stage of the language. Traces of ablaut are found in all modern Indo-European languages, though its prevalence varies greatly.