Other forms: ablauts
Ablaut is a linguistic term that refers to the changing of vowel sounds within a word to indicate a shift in grammatical function, like in drive, drove, and driven.
While most modern English verbs simply add -ed to the end of a word to make it past tense — such that walk becomes walked and had walked — other English verbs are irregular: e.g., take, took, and taken. This is due to ablaut, which dates back thousands of years to Proto-Indo-European, the common ancestor of English, Latin, Greek, and Sanskrit. In Indo-European languages, such variation of vowels to indicate changes in tense or number is common, and it remains in English for some verbs, like sing, sang, and sung. The term ablaut originates from the German words ab, meaning "off," and laut, meaning "sound."