ablaut (n.)

"systematic vowel alteration in the root of a word to indicate shades of meaning or tense," a characteristic of Indo-European languages, 1849, from German Ablaut, literally "off-sound" ("off" here denoting substitution), coined by J.P. Zweigel in 1568 from ab "off" (from Old High German aba "off, away from," from PIE root *apo- "off, away") + Laut "sound, tone" (from Old High German hlut, from Proto-Germanic *hludaz "heard, loud," from suffixed form of PIE root *kleu- "to hear"). The word was popularized by Jakob Grimm. The process is what makes strong verbs in Germanic. An example is bind/band/bond/bound + (German) Bund.

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