Ablaut

имя существительное; лингвистика аблаут

Большой англо-русский словарь

Ablaut

noun Etymology: German, from ab away from + Laut sound a systematic variation of vowels in the same root or affix or in related roots or affixes especially in the Indo-European languages that is usually paralleled by differences in use or meaning (as in sing, sang, sung, song)

Энциклопедический словарь Мерриама-Вебстера