Ü

Ü (lowercase ü) is a Latin script character composed of the letter U and the diaeresis diacritical mark. In some alphabets such as those of a number of Romance languages or Guarani it denotes an instance of regular U to be construed in isolation from adjacent characters with which it would usually form a larger unit; other alphabets like the Azerbaijani, Estonian, German, Hungarian and Turkish ones treat it as a letter in its own right. In those cases it typically represents a close front rounded vowel.

Although not a part of their alphabet, Ü also appears in languages such as Finnish and Swedish when retained in foreign proper names like München ("Munich"). A small number of Dutch and Afrikaans words employ the character to mark vowel hiatus (e.g. reünie /reːyˈni/ ("reunion"), a loanword marked with diaeresis to suppress the native reading of eu as a digraph pronounced /øː/).

U-umlaut
A glyph, U with umlaut, appears in the German alphabet. It represents the umlauted form of u, which results in when long and  when short. The letter is collated together with U, or as UE. In languages that have adopted German names or spellings, such as Swedish, the letter also occurs. It is however not a part of these languages' alphabets. In Swedish the letter is called tyskt y which means German y.

Though not a part of the Slovene alphabet, ü is often used in eastern Styrian dialects, especially around Ptuj as well as in the Resian dialect with the same pronouncation as in German.

In other languages that do not have the letter as part of the regular alphabet or in limited character sets such as ASCII, U-umlaut is frequently replaced with the two-letter combination "ue". Software for optical character recognition sometimes sees it falsely as ii.

Letter Ü
The letter Ü is present in the Hungarian, Turkish, Uyghur Latin, Estonian, Azeri, Turkmen, Crimean Tatar, Kazakh Latin and Tatar Latin alphabets, where it represents a close front rounded vowel. It is considered a distinct letter, collated separately, not a simple modification of U or Y, and is distinct from UE.

Wayuu represents the close central unrounded vowel using this letter.

In the Swedish, Danish, Norwegian and Finnish alphabets ü is alphabetized as y.

It is not present in the Basque alphabet but the Souletin dialect uses it for.

This same letter appears in the Chinese Romanisations Pinyin, Wade–Giles, and the German-based Lessing-Othmer, where it represents the same sound : 綠/lǜ (green) or 女/nǚ (female). Standard Mandarin Chinese pronunciation has both the sounds and. Pinyin only uses "Ü" to represent after the letters "L" or "N" to avoid confusion with words such as 路/lù (road) and 怒/nù (anger). Words such as 玉/yù (jade) or 句/jù (sentence) are pronounced with, but are not spelled with "Ü", although Wade–Giles and Lessing use "Ü" in all situations. As the letter "Ü" is missing on most keyboards and the letter "V" is not present in standard Mandarin pinyin, the letter "V" is used on most computer Chinese input methods to enter the letter "Ü". As a result, romanisation of Chinese with the letter "V" representing the Ü sound is sometimes found. However, Ü sound should be officially represented by "yu" in Pinyin when it is difficult to enter Ü. For example, the surname Lü (吕) would be written as "Lyu" in passports. Four extra tones for the letter "ü", which are "ǖ, ǘ, ǚ, ǜ", is added in Unicode as per GB/T 2312.

U-diaeresis
Several languages use diaeresis over the letter U to show that the letter is pronounced in its regular way, without dropping out or building diphthongs with neighbouring letters.

In Catalan, ü is used in the letter combinations güe, güi, qüe and qüi to indicate the pronunciation, , or , respectively (e.g. nicaragüenc, pingüins, qüestió, aqüicultura); this contrasts with the combinations gue/gui/que/qui, in which the u is silent. Catalan also uses the letter ü to indicate that a vowel pair that would normally form a diphthong must be pronounced as separate syllables (e.g. baül, diürna).

Similarly, in Spanish, ü is used in the combinations güe and güi, to distinguish them from "gue"  and "gui"  (e.g. nicaragüense, pingüinos). Unlike Catalan, though, Spanish does not use it after q, instead using cue and cui to spell words with or  sounds (cuestión, acuicultura); it also does not use it to break diphthongs, sometimes using the letter ú for that purpose when necessary (baúl, but diurna).

In French, the diaeresis appears over the "u" only very rarely, in some uncommon words, capharnaüm ('shambles'), Capharnaüm/Capernaüm  or Emmaüs. After the 1990 spelling reforms, it is applied to a few more words, like aigüe (formerly aiguë), ambigüe (formerly ambiguë) and argüer  (formerly without the diaeresis).

Usage in phonetic alphabets
In the Rheinische Dokumenta, a phonetic alphabet for many West Central German, Low Rhenish, and related vernacular languages, "ü" represents a range from to.

Typography
Historically the unique letter Ü and U-diaeresis were written as a U with two dots above the letter.

U-umlaut was written as a U with a small e written above (Uͤ uͤ): this minute e degenerated to two vertical bars in medieval handwritings. In most later handwritings these bars in turn nearly became dots.

In modern typography there was insufficient space on typewriters and later computer keyboards to allow for both a U-with-dots (also representing Ü) and a U-with-bars. Since they looked near-identical the two glyphs were combined, which was also done in computer character encodings such as ISO 8859-1. As a result, there was no way to differentiate between the three different characters. While the distinction can be recreated in modern Unicode using combining diacritics, modern typographic standards do not recommend doing so. In the Hungarian alphabet, double acute U (Ű) is a distinct letter representing a long Ü.

Keyboarding
The methods available for entering $\langleÜ\rangle$ and $\langleü\rangle$ from the keyboard depend on the operating system, the keyboard layout, and the application.
 * Microsoft Windows – some keyboard layouts feature separate keys for $\langleÜ\rangle$
 * Using the Swiss French keyboard, $\langleü\rangle$ can be entered by typing Shift
 * Using the US International layout, $\langleü\rangle$ can be entered by typing AltGR
 * Microsoft Windows: with the Number Lock on, hold down the Alt key while typing on the numeric keypad the decimal value of the code point from the active DOS/OEM code page without a leading zero, then release the Alt key; i.e. Alt for $\langleÜ\rangle$ and Alt for $\langleü\rangle$
 * Microsoft Windows: with the Number Lock on, hold down the Alt key while typing on the numeric keypad the decimal value of the code point from the active ANSI code page with a leading zero, then release the Alt key; i.e. Alt for $\langleÜ\rangle$ and Alt for $\langleü\rangle$
 * Microsoft Word for Windows: type Ctrl followed by Shift for $\langleÜ\rangle$ or Ctrl then U for $\langleü\rangle$
 * macOS with an English keyboard layout (Australian, British, or U.S.): type Option followed by Shift for $\langleÜ\rangle$ or Option and then U for $\langleü\rangle$ or by keeping the U key pressed and then typing 2
 * In Linux-based operating systems, this symbol may be typed by pressing the Compose key followed by u, ".
 * In GTK-based GUI-Applications, Ctrl followed by the Hex-Code