U with Umlaut: ü in German, Turkish, Spanish güe and Pinyin

Is the ü an umlaut or a diaeresis?

The u with umlaut and the u with two dots are one character, U+00FC. Unicode names it U WITH DIAERESIS in every language, so German über and Spanish pingüino share it. The language decides what the dots do. German uses them as an umlaut that changes the vowel. Spanish and French use them as a diaeresis: say this vowel. In Turkish, Hungarian and Estonian, ü is a letter with its own slot in the alphabet.

Language	What the dots do	Example	Where ü goes in a sorted list
German	Umlaut: /yː/ in für, /ʏ/ in müssen	für, über, würde	Next to u
Spanish	Diaeresis: the u after g is said as /w/	vergüenza, pingüino	Next to u
French	Diaeresis: the vowel is said on its own	ambigüe	Next to u
Catalan	Diaeresis: two vowels, two syllables	taüt (coffin)	Next to u
Turkish	A letter of its own, /y/	Üsküdar, Süleyman	Its own letter, right after u
Hungarian	A letter of its own, [y]	Tünde	Its own letter after u, with ű beside it
Estonian	A letter of its own, named üü	Ülo, Ülle	Near the end, before x
Mandarin pinyin	Tells ü apart from u	nü, lü

The meanings come from Wiktionary's entry for ü and from FundéuRAE. The German sounds are WikiPron transcriptions. Names and places come from Wikidata and GeoNames.

The sort column follows the Unicode CLDR collation rules. The Turkish (opens in a new tab) rule reads &U<ü<<<Ü, a new letter after u. The Hungarian (opens in a new tab) rule adds ű as a variant of ü. The Estonian (opens in a new tab) rule puts õ, ä, ö and ü right before x. German, Spanish, French and Catalan have no rule for ü. The Unicode Collation Algorithm (opens in a new tab) then files it with u.

So a list sorted by Turkish rules puts Üsküdar after every word that starts with a plain U. German rules keep über among the u words. In Turkish, Hungarian and Estonian, an umlaut u typed without its dots is a different letter. It is not a sloppy spelling. Turkish has written the letter since Law 1353 (opens in a new tab), accepted on 1 November 1928: the table attached to the law prints Ü and ü as a letter pair of the new alphabet, right after U and u.

Why does Spanish write ü in pingüino and vergüenza?

Without the dots, the u in gue and gui would be silent. In Spanish, gu before e or i is a hard g, and the u is only spelling. FundéuRAE (opens in a new tab), advised by the Real Academia Española, says the diéresis shows that this u must be pronounced. Its examples are vergüenza and pingüino. So the Spanish u with dots is no German umlaut, and Spanish sorting files it with u.

Wiktionary's transcriptions show the difference in one column.

Spelling	Word	Meaning	Wiktionary IPA	Is the u said?
gue	guerra	war	/ˈɡera/	No
gui	guiso	stew	/ˈɡiso/	No
güe	vergüenza	shame	/beɾˈɡwenθa/	Yes, as /w/
güi	pingüino	penguin	/pinˈɡwino/	Yes, as /w/

The dots can come and go inside one word family. The verb averiguar, to find out, is /abeɾiˈɡwaɾ/. Before an a, the u is heard without help. Its form averigüe keeps that /w/ only because it is spelled with ü. Without the dots, a reader would say averigue like guiso, with no /w/.

FundéuRAE adds a rarer use. Poets may put the dots on the first vowel of a pair to split it into two syllables. So rüido is read ru-i-do.

What does ü change in a German word?

German is where the u with an umlaut earns its name. The dots change the vowel itself, and that change often carries grammar. A plural, a comparative or a verb form can differ from its base only by the ü. Wiktionary transcribes Fuß, foot, as /fuːs/ and its plural Füße as /ˈfyːsə/. The long u turns into a long ü.

Base word	With ü	What the ü marks
Mutter	Mütter	the plural
Fuß	Füße	the plural
jung	jünger	the comparative
wurde	würde	subjunctive II of werden

Sometimes the dots separate two words with nothing in common. Wiktionary gives schwül as sultry or muggy weather, /ʃvyːl/. Schwul is a colloquial word for gay, /ʃvuːl/. Both vowels are long, and only the dots tell the words apart.

The u with umlaut also fills everyday German. FrequencyWords ranks für, über, müssen and würde among the most frequent words in German subtitles.

How is ü written and typed in Chinese pinyin?

In pinyin the umlaut u stands for a vowel distinct from u, but it does not always keep its dots. The Scheme for the Chinese Phonetic Alphabet (opens in a new tab), published by China's Ministry of Education, sets the spelling rules.

Where ü stands	How it is written	Dots	Examples in the Scheme
At the start of a syllable	yu, yue, yuan, yun	Dropped	迂 yu, 约 yue
After j, q or x	ju, qu, xu	Dropped	居 ju, 区 qu
After n or l	nü, lü	Kept	女 nü, 吕 lü

So nü and lü are where you see the dots in practice. A tone mark sits on top of them: Wiktionary (opens in a new tab) writes 女, woman, as nǚ. The tone-marked forms ǖ ǘ ǚ ǜ are characters of their own, U+01D6, U+01D8, U+01DA and U+01DC, encoded since Unicode 1.1 in 1993. They are in the list of u letters further down.

Typing is the other half. The same Scheme keeps the letter v for loanwords, minority languages and dialects only, so standard Mandarin leaves it free. Apple's guide to Pinyin - Simplified (opens in a new tab) says Full Pinyin uses v in place of ü. So on a Mac's Pinyin keyboard, a u with umlaut is typed as v. Type lv and pick 绿 from the candidates.