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, represents a schwa. Such dots are also sometimes used for stylistic reasons (as in the family name Brontë or the band name Mötley Crüe). In modern computer systems using Unicode, the two-dot diacritics are almost always encoded identically, having the same code point. For example, represents both a-umlaut and a-diaeresis. Their appearance in print or on screen may vary between typefaces but rarely within the same typeface. Uses Diaeresis The "diaeresis" diacritic is used to mark the separation of two distinct vowels in adjacent syllables when an instance of diaeresis (or hiatus) occurs, so as to distinguish from a digraph or diphthong. For example in the spelling "coöperate", the diaeresis reminds the reader that the word has four syllables co-op-er-ate, not three. It is used in several languages of western and southern Europe, though rarely now in English. Umlaut The "umlaut" diacritic indicates a sound shift phenomenon also known as umlaut in which a back vowel becomes a front vowel. It is a specific phenomenon in German and other Germanic languages, affecting the graphemes , , and , which are modified to , , and . Stylistic use The two dot diacritic is also sometimes used for purely stylistic reasons. For example, the Brontë family, whose surname was derived from gaelic and had been anglicised as "Prunty", or "Brunty": At some point, the father of the sisters, Patrick Brontë (born Brunty), decided on the alternative spelling with a diaeresis diacritic over the terminal to indicate that the name had two syllables. Similarly the "metal umlaut" is a diacritic that is sometimes used gratuitously or decoratively over letters in the names of hard rock or heavy metal bandsfor example, those of Motörhead and Mötley Crüe, and of parody bands, such as Spın̈al Tap. Other uses by language A double dot is also used as a diacritic in cases where it functions as neither a diaeresis nor an umlaut. In the International Phonetic Alphabet (IPA), a double dot above a letter is used for a centralized vowel, a situation more similar to umlaut than to diaeresis. In other languages it is used for vowel length, nasalization,