Two interesting examples of umlaut involve vowel distinctions in Germanic verbs.
From the en.wikipedia.org
When referred to as U-umlaut, it typically represents a close front rounded vowel.
From the en.wikipedia.org
At some point, he topped his surname with an umlaut and began calling himself Jose.
From the boston.com
A variation of Furtwangler's name without the umlaut is spelled Furtwaengler.
From the npr.org
German orthography is generally consistent in its representation of i-umlaut.
From the en.wikipedia.org
Instead, i-umlaut of ea and rare eo is spelled e, and i-umlaut of io remains as io.
From the en.wikipedia.org
In the case of u-umlaut, this entails labialization of unrounded vowels.
From the en.wikipedia.org
Sometimes, there's a need to distinguish between the umlaut sign and the diaeresis sign.
From the en.wikipedia.org
This is because all the later dialects have regular umlaut of both long and short vowels.
From the en.wikipedia.org
More examples
A diacritical mark (two dots) placed over a vowel in German to indicate a change in sound
An umlaut is the orthographical representation of a type of sound shift in spoken language. A very similar diacritical mark (called diaeresis or "trema") is used to signify a linguistic hiatus. ...
In linguistics, umlaut (from German um- "around"/"the other way" + Laut "sound") is a process whereby a vowel is pronounced more like a following vowel or semivowel. The term umlaut was originally coined and is principally used in connection with the study of the Germanic languages. ...
"u00C4" and "u00E4" are both characters that represent either a letter from several extended Latin alphabets, or the letter A with an umlaut mark or diaeresis.
N : 1. the change of a vowel that is caused by partial assimilation to a succeeding sound or that occurs as a reflex of the former presence of a succeeding sound which has been lost or altered (as to mark pluralization in goose, geese or mouse, mice). 2. ...
(1) Jacob Grimm's term for the process of assimilating a vowel to another sound in the following syllable. This process is also called mutation. This process is responsible for many unusual plurals in Germanic languages like English--such as man-men, foot-feet, and so on. ...
[phonetics,phonology] A significant sound change in the Germanic languages whereby a back vowel was shifted to a front articulation in anticipation of an /i/ or /j/ in the following syllable. ...
A kind of vowel mutation that consists in the change of a vowel into another influenced by some feature of a vowel in the following syllables. ...