[ahb-lout, ab-; Ger. ahp-lout] 
| (in Indo-European languages) regular alternation in the internal phonological structure of a word element, esp. alternation of a vowel, that is coordinated with a change in grammatical function or combination, as in English sing, sang, sung, song; apophony. |
| ab·laut (äb'lout', äp'-) n. A vowel change, characteristic of Indo-European languages, that accompanies a change in grammatical function; for example, i, a, u in sing, sang, sung. Also called gradation. [German : ab, off (from Middle High German ab, abe, from Old High German aba; see apo- in Indo-European roots) + Laut, sound (from Middle High German lūt, from Old High German hlūt; see kleu- in Indo-European roots).] |