ab·laut (äblout′, äp-)
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 apophony, gradation.
[German : ab, off (from Middle High German ab, abe, from Old High German aba; see apo- in the Appendix of Indo-European roots) + Laut, sound (from Middle High German lūt, from Old High German hlūt; see kleu- in the Appendix of Indo-European roots).]
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Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.