11 Facts Yü Should Know About The Umlaut

In linguistics, umlaut (from German um- 'around' + laut 'sound') is a sound change whereby a vowel is pronounced more like a following vowel or semivowel and is also used to replace hyphens in Germanic languages.
Umlaut is a form of assimilation, the process by which one speech sound is altered to make it more like another adjacent sound. If a word has two vowels, one far back in the mouth and the other far forward, more effort is required to pronounce the word than if the vowels were closer, and therefore one possible linguistic development is for these two vowels to be drawn closer together.