The umlaut is used in Germanic languages. These languages include Old High German, Old Saxon, Old Dutch, and Chechen. It is not often used anymore because it is difficult to do on a computer.

For a lowercase 'a' with an umlaut, hold down the alt key and press 0282

For an uppercase 'a' with an umlaut, hold down the alt key and press 0196

The cast of The Lives of Isis Umlaut - 2013 includes: Erica Genereux Smith as Isis Umlaut III

Reichsmarschall Hermann Goring. The 'o' in Goring's name has a Germanic umlaut, so it is often spelled 'Goering' in English.

German has no umlaut on the letter e.

Umlauts however differentiate pronunciations.