Ü

Ü (lowercase ü) is a letter of the Latin script formed by adding two dots, the diaeresis, above the letter U. It appears in the alphabets of German, Turkish, Hungarian, Estonian, Spanish, Azerbaijani, Turkmen, and many other languages, where it serves two distinct functions: in some languages it is an independent letter representing a front rounded vowel, and in others it is a variant of u used to resolve ambiguity in pronunciation.^{1 • 2}

Unicode identity and encoding

Ü is encoded as U+00DC in the Latin-1 Supplement block (U+0080 to U+00FF), with its lowercase counterpart ü at U+00FC. Both were added in Unicode version 1.1 in June 1993.^{1 • 3} The character is classified as an uppercase letter (category Lu) of the Latin script, with left-to-right bidirectional behavior and no mirroring.⁴

The letter can be written two ways that Unicode considers canonically equivalent: as the single precomposed code point U+00DC, or as the base letter U (U+0055) followed by the combining diaeresis U+0308. The Unicode Standard includes precomposed forms such as U+00DC for compatibility with existing standards, and provides a mapping between the two spellings, so text normalized under NFC or NFD compares equal either way.^{1 • 7} In UTF-8, Ü is the two-byte sequence 0xC3 0x9C; in HTML it can be written as Ü or with the named entity Ü.⁴

Beyond the basic letter, Unicode encodes a small family of combinations that add a second mark, including Ǖ (U+01D5, U with diaeresis and macron), Ǘ (U+01D7, with acute), Ǚ (U+01D9, with caron), and Ǜ (U+01DB, with grave).³

Umlaut and diaeresis: one shape, two roles

The two dots over Ü look identical in the two roles the letter plays, but they mark different things. In German, ü is one of the umlaut letters (Ä, Ö, Ü), which arose from a historical sound change in which a back vowel was fronted under the influence of an i or j in the following syllable; the umlaut changes the quality of the vowel itself, so German u becomes ü as a different sound.^{2 • 8} In French, Spanish, Dutch, and traditional English usage, the same mark is a diaeresis (French tréma), which signals that two adjacent vowels belong to separate syllables, as in naïve or Noël; it does not change the value of the vowel it sits on.²

Unicode names the character "U with diaeresis" regardless of which role it plays in a given language, so the same code point serves German umlaut spelling and Spanish or French diaeresis spelling alike.¹ This shared encoding has practical consequences: German bibliographic standards distinguish umlaut from trema for sorting purposes, and proposals have been made to encode the distinction explicitly, because the two diacritics behave differently in sorting even though they look the same.⁹

Languages that use Ü

The decodeunicode database, drawing on Unicode 11.0.0 and CLDR data, lists Ü in the main set of letters for German, Turkish, Hungarian, Estonian, Spanish, Catalan, Galician, Asturian, Turkmen, Azerbaijani, Welsh, Dutch, Low German, Swiss German, Kölsch, Sango, Volapük, and West Frisian, with a much larger auxiliary set including Danish, Swedish, Norwegian, Finnish, Portuguese, Italian, and Afrikaans.¹⁰

German. Ü is one of the three umlaut letters, treated in German toponymic practice as a diacritic letter alongside Ä and Ö and the letter ß.⁶ It represents a front rounded vowel, formed by rounding the lips as for u while positioning the tongue as for e.¹¹ When the character is unavailable, for example in older domain names or international identifiers, German convention writes ue instead.⁶

Turkish. Ü is one of seven letters of the Turkish alphabet that English does not have, alongside ç, ş, ğ, ı, İ, and ö.⁵

Spanish. Spanish is the restricted case: u is the only vowel that can carry the diaeresis. The letter u is normally silent between g and e or i (guerra, guitarra), and the diaeresis signals the exceptional case in which it is pronounced, as in pingüino or vergüenza.²

Azerbaijani. Ü is a letter of the Azerbaijani Latin alphabet, and the language's official orthoepy norms give pronunciation rules that refer to it directly, for example in words such as mübarək and tədarük.¹²

Typing and practical use

On Windows, Ü can be typed by holding Alt and entering 0220 on the numeric keypad (or Alt+0252 for lowercase ü); on macOS, the Unicode Hex Input keyboard accepts the hexadecimal value directly.^{4 • 13} In markup and programming contexts the character is available as the HTML entity Ü, the CSS escape \00DC, and the JSON or JavaScript escape \u00DC.³

The letter also illustrates a broader point about diacritics and language technology: cross-linguistic studies of diacritic complexity find that measurable properties of how a writing system uses diacritics, including their frequency and ambiguity, correlate with how well diacritic restoration models perform, so characters like Ü sit at the intersection of orthography and computational linguistics rather than being merely typographic decoration.¹⁴

References

1. Ü U+00DC Latin Capital Letter U with Diaeresis, UnicodeCharacter
2. How to Type Umlaut (¨, ä, ö, ü, ë, ï, ÿ...), WayToType
3. Unicode Character "Ü" (U+00DC), UnicodePlus
4. Unicode Character 'LATIN CAPITAL LETTER U WITH DIAERESIS' (U+00DC), fileformat.info
5. Names, Turkish characters and transliteration, Hacettepe University
6. Toponymic Guidelines (Germany), UN Group of Experts on Geographical Names
7. The Unicode Standard, Version 18.0.0, Chapter 2: Dynamic Composition and Equivalent Sequences
8. The History of the Umlaut and the Diaeresis, Babbel Magazine
9. Proposal to encode LATIN VARIATION SELECTOR UMLAUT and TREMA, ISO/IEC JTC1/SC2/WG2 N2593
10. Ü, U+00DC, decodeunicode.org
11. U+00DC Latin Capital Letter U with Diaeresis, unicodecharacter.org
12. Azərbaycan dilinin orfoepiya normaları, Cabinet of Ministers of Azerbaijan, Decision No. 175 (2021)
13. FAQ: Fonts and Keyboards, Unicode Consortium
14. Adi Cohen and Yuval Pinter, The Degree of Language Diacriticity and Its Effect on Tasks, arXiv

Topic: Encyclopedia › Society and history › Languages and linguistics › Writing and notation systems › Latin script

Initially written Sep 17, 2026 · Reviewed: Oct 25, 2026 · Edited: Oct 15, 2026; Oct 25, 2026 · Last review: Oct 25, 2026

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