For example, the German noun Mann [man] ("man"), with the a pronounced as in English "father", becomes Männer [m'En@r, m'En6] in the plural, with the ä pronounced like the ai in "hair", a front vowel sound that is assimilated to the vowel in the -er suffix. The original conditioning environment in German was an i or j in the following syllable (the plural suffix originally was -ir). Later, umlaut acquired a grammatical function and was extended by analogy, for example to form plurals like Ofen ['o:f@n] / Öfen ['2:f@n] ("oven"/"ovens"). Note that English, being a Germanic language, has preserved some of these changes in irregular inflected forms such as man/men, tooth/teeth, long/length, old/elders, etc., even though it has lost the suffixes that originally caused them, and has changed their spelling.
An umlaut should be distinguished from a change in vowel indicating a difference in grammatical function, called an ablaut, as in sing/sang/sung. Ablaut originated in the Proto-Indo-European language, whereas umlaut originated later, in Proto-Germanic. These terms may also be used for similar changes in other language families.
The word is also used to refer to the diacritic mark composed of two small dots placed over a vowel (¨) to indicate this change in German and Hungarian (the same mark is used to indicate diaeresis in other languages). The origin of the graphical symbol lies in the following e, which was originally written above in tiny form. In handwritings of the Middle-ages until (in Germany) 1941, the e looked like two tiny strokes (compare the Sütterlin "e"). In script form this simplified to two bars above the letter. These bars became confused with the diaeresis, and are now normally written as two small dots above. The Hungarian umlauts are ö and ü; the German ones are ä, ö, and ü. Their respective pronunciation is similar in both languages.
In Finnish and North Germanic languages (i.e., Danish, Icelandic, Norwegian and Swedish) characters (ü, ä, ö, and å) looking similar to German umlauts are in fact considered letters in their own right, despite their representing sounds similar to the corresponding sounds in German. As it is not a case of marking grammatical variation, i.e., of tempus or modus, nor of syllable modification, it is in fact neither a case of umlaut nor of diacritical marking. Hence it ought to be improper to call these characters umlauts; however, there is no more precise descriptor in English.
When typing in German, if umlaut letters are not available, they are usually replaced by the underlying vowel and a following e. In Switzerland, capital umlauts are usually printed as digraphss, i.e., Ae, Oe, Ue, since they are generally not used nor included on Swiss keyboards.
In HTML umlauts are circumscribed with an
&?uml; entity. All umlauts, as well as the ess-tsett (another letter used in German, although not an umlaut included here for reference), are part of the ISO-8859-1 character set and thus have the same codepoints in ISO-8859-1 and Unicode. See the following table:
|Character||Replacement||HTML entity||Unicode/ISO-8859-1 codepoint|
There are a few exceptions where German oe or ue do not represent ö and ü, respectively. For example, Tuer [t'u:@r, t'u:6] ("doer") and Tür [ty:r] ("door") are distinct; soeben [zO'e:b@n, zO'e:bn=] ("just now") has three syllables and is not söben; Otto von Guericke [g'e:rIk@] is not Güricke (this proper name stems from French). German does not use the diaeresis to distinguish disyllabic oe from ö, etc.