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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.

n. The substitution of one root vowel for another, thus indicating a corresponding modification of use or meaning; vowel permutation; as, get, gat, got; sing, song; hang, hung.

n. In philology, a substitution of one vowel for another in the body of the root of a word, accompanying a modification of use or meaning: as, bind, band, bound, bond, German bund; more especially, the change of a vowel to indicate tense-change in strong verbs, instead of the addition of a syllable (-ed), as in weak verbs: as, get, gat, got; sink, sank, sunk.

n. a vowel whose quality or length is changed to indicate linguistic distinctions (such as sing sang sung song)

"They exhibit perfectly the features of quantitative ablaut, which is the older form."

vowel    vowel sound   

gradation    grade   

ablauting   

voj    apophony    gradation    prij    l    sh    alternation    prijevoj