ablaut

Ablaut and vowel gradation

Ablaut is the oldest and most extensive single source of vowel gradation in the Indo-European languages and must be distinguished clearly from other forms of gradation, which developed later, such as Germanic umlaut (man / men, goose / geese, long / length) or the results of modern English word-stress patterns (man / woman, photograph / photography). Confusingly, in some contexts, the terms 'ablaut', 'vowel gradation', 'apophony' and 'vowel alternation' are used synonymously, especially in synchronic comparisons, but historical linguists prefer to keep 'ablaut' for the specific Indo-European phenomenon, which is the meaning intended by the linguists who first coined the word.