ů versus ú: Two Ways to Write Long u

Czech writes the long vowel [uː] — a drawn-out oo as in English moon — in two different ways: ú (called u s čárkou, "u with an acute") and ů (called u s kroužkem, "u with a little ring"). Here is the catch that throws every learner at first: they sound exactly the same. There is no audible difference whatsoever. The choice between them is a pure spelling convention, and unlike most of Czech spelling — which is gloriously phonetic, one letter to one sound — this is one of the rare places where you have to know a rule that your ears can't help you with.

The good news is that the rule is almost entirely positional: it depends on where in the word the long u sits. Get the position right and you get the spelling right, every time.

The core rule: where the long u lives in the word

A single word can show both at once. Take úkol (a task, a piece of homework). In the genitive plural it becomes úkolů — it starts with ú because that is the front of the word, and it ends with ů because that is the end. One word, both spellings, identical pronunciation.

ú — at the front

Word-initial long u is always written ú. This is extremely common because Czech has a whole family of words built on the prefix ú- and on roots that begin with a long u.

The same applies after a prefix, because a prefix doesn't change where the root begins — the root still "starts," even though it is no longer the first letter of the whole word. So a root that would take ú on its own keeps that ú after a prefix glues onto the front.

ů — in the middle and at the end

Everywhere else — once the long u is not at the start of a word or root — you write ů, the one with the ring. This covers a huge number of the most basic words in the language.

Notice domů: the long u at the end of a word is written ů. The same goes for dolů (downwards) and other direction words — final long u is never spelled -ú.

Why the ring exists — and why it can't start a word

This is one of those spellings that makes much more sense once you know where it came from. The little ring is not decorative: it is a fossilized letter o. Centuries ago this sound was a diphthong, uo [uo], which had developed out of an older long ó. Over time the uo contracted into a single long [uː], but the spelling kept a memory of the vanished o by perching a tiny o on top of the u — and that is the ring you see today, ů. You can still hear the original uo in some Moravian dialects, where kůň (horse) is pronounced something like kuoň.

This history explains the one fact that makes the rule predictable: because the uo diphthong never arose at the beginning of a word, the ring never appears word-initially. There simply was no uo to contract there. Word-initial long u comes from a different, older source and keeps the plain acute ú. So the positional rule isn't arbitrary at all — it traces two genuinely different historical origins of the same modern sound.

The one exception: loanwords keep ú

Foreign words borrowed into Czech were spelled with ú when they came in, and they keep it even in the middle of the word, where a native word would have ů. There aren't many, but two are common and worth memorizing because they look like they "break" the rule:

This produces a lovely near-trap. kúra (a course of treatment) and kůra (bark, peel, rind) are pronounced identically — both [kuːra] — but spelled differently, because one is a loanword and the other is native Czech.

For an English speaker this is genuinely odd: you are distinguishing two words you cannot hear apart, purely by their history. There is no shortcut — you simply learn that kúra/túra/fúze and a handful of other borrowings keep the acute inside the word.

A note on pronunciation versus spelling

Do not let any of this make you think there are two long-u sounds. There is one sound, [uː], and it is just the short u held longer — exactly the relationship between short and long covered on the vowel length page. The ring and the acute are both simply length marks on u; they tell you the vowel is long, and the shape of the mark (ring vs. acute) only tells you the spelling tradition. When you read aloud, treat ú and ů as one and the same drawn-out oo. The choice only matters when you write. For drilling the writing rule itself with more examples and practice, see the spelling page on ú vs ů.

Common mistakes

Key takeaways

• ú and ů sound the same — both are long [uː]. The difference is spelling, not pronunciation.
• ú at the front — word-initially and at the start of a root after a prefix: úkol, únor, neúplný, trojúhelník.
• ů in the middle and at the end — dům, stůl, kůň, můj, domů.
• The ring is a fossilized o from an old uo diphthong, which is exactly why it can never start a word.
• Loanwords keep ú even mid-word: kúra, túra — beware the pair kúra (treatment) vs kůra (peel).