German: The umlaut is a key part of German orthography, modifying the vowels a, o, and u, changing their pronunciation.
* ä is pronounced like the "e" in "bed"
* ö is pronounced like the "o" in "word"
* ü is pronounced like the "u" in "rule"
Swedish: The umlaut is used for vowels a, o, and u, but it's not as widespread as in German. It can change the pronunciation slightly, but it's often optional.
Finnish: The umlaut is used for vowels a, o, and u, changing their pronunciation. The umlaut is written as ä and ö but not ü.
Hungarian: The umlaut is used for the vowel ö, pronounced like the "o" in "word."
Estonian, Latvian, Lithuanian: The umlaut is used for the vowel ä and sometimes ö, changing their pronunciation.
Turkish: The umlaut is used for the vowels ü and ö, pronounced like the "u" in "rule" and the "o" in "word," respectively.
Other languages: While the umlaut is not a standard feature in most languages, it can sometimes be used in writing foreign words, especially when transliterating German words.
Important note: The umlaut is not always written as a double dot (¨). In some languages, it might be written as a circle (°) or a diacritical mark placed below the letter (e.g., ă, ŏ, ŭ).