a. A change in a vowel sound caused by partial assimilation especially to a vowel or semivowel occurring in the following syllable.
b. A vowel sound changed in this manner. Also called vowel mutation.
2. The diacritic mark (¨) placed over a vowel to indicate an umlaut, especially in German.
tr.v. um·laut·ed, um·laut·ing, um·lauts
1. To modify by umlaut.
2. To write or print (a vowel) with an umlaut.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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.