Diacritical marks of two dots ¨, placed side-by-side over or under a letter, are used in a number of languages for several different purposes. The most familiar to English-language speakers are the diaeresis and the umlaut, though there are numerous others. For example, in Albanian, ë represents a schwa. Such diacritics are also sometimes used for stylistic reasons.

Umlaut is a name for the two dots diacritical mark as used to indicate in writing the result of the historical sound shift due to which former back vowels are now pronounced as front vowels.