The Chōonpu (ー): Katakana Long Vowels

Katakana has an elegant shortcut for writing long vowels that hiragana lacks: a single horizontal bar, ー, called the chōonpu (長音符, "long-sound mark"). Instead of spelling out a second vowel kana, katakana just draws a line and says "hold the previous vowel for one more beat." So コーヒー is kōhī, ケーキ is kēki, スーパー is sūpā. The bar is small, but the beat it adds is a full mora — and, as with all vowel length in Japanese, that beat can change the meaning of the word.

One bar, any vowel

The beauty of the chōonpu is that it is vowel-neutral. The same bar lengthens a, i, u, e, or o — it simply extends whatever vowel came immediately before it. This is why one symbol replaces the five different vowel-kana strategies that hiragana needs.

Notice スーパー carries two bars — one after ス and one after パ — because both vowels are long: sū-pā. A word can hold as many chōonpu as it has long vowels.

Why katakana needs a special device

Hiragana already has a perfectly good way to write long vowels — it adds a vowel kana (ああ, いい, うう, and the えい/おう conventions), covered on the long vowels in hiragana page. So why does katakana use a bar instead?

The answer is that katakana's main job is loanwords, and loanwords come from languages whose vowel lengths do not line up with the えい/おう spelling logic. A bar sidesteps all of that: it marks "long vowel here" directly, regardless of which vowel it is, and regardless of any historical spelling. It is cleaner and unambiguous — exactly what you want for a script that has to render thousands of imported words.

In practice, the chōonpu is used almost exclusively in katakana. You will occasionally see it in hiragana on shop signs, in manga, or in playful text to stretch a sound — らーめん on a ramen shop's banner, or a drawn-out ええーっ of surprise — but that is a stylistic, (informal) effect. In ordinary hiragana writing, long vowels are spelled with vowel kana, not the bar.

The bar is length — and length is meaning

Here is the point English speakers most need to absorb: the chōonpu is a full mora of vowel length, not punctuation. It is not a dash, not a hyphen, not a stylistic flourish you can drop. Leaving it out changes the word, because — as everywhere in Japanese — vowel length is phonemic.

The cleanest proof is a real minimal pair from everyday life:

The only difference is the bar. Ask for a cold ビル and you have asked for a cold building; ask for a cold ビール and you get your beer.

The same logic explains a famous English-to-katakana pair. English "car" ends in a long vowel; "ka" does not. Japanese captures that difference with — and only with — the bar:

Length is the entire distinction. This is why the bar is not optional decoration — it is carrying the same weight a whole extra letter would carry in English.

In vertical writing, the bar stands up

Japanese can be written vertically (縦書き) as well as horizontally, and the chōonpu adapts to the direction of the text. In horizontal writing it is a horizontal line, ー. In vertical writing, it rotates ninety degrees to a vertical stroke — a short "|" running in the same direction as the column of characters. It is the same mark doing the same job; only its orientation follows the flow of the text. Do not mistake the vertical form for the number one or the katakana ノ — in a column of katakana, a vertical stroke after a vowel is the chōonpu lengthening that vowel.

Common mistakes

The two errors to guard against are dropping the bar (writing コヒ, ケキ, ビル for coffee, cake, beer) and reading it as a dash or hyphen. Both come from not yet feeling that a lengthened vowel is a distinct, meaningful sound in Japanese. Hold each bar for a genuine extra beat and these mistakes disappear.

Key takeaways

• The chōonpu (ー) lengthens whatever vowel precedes it — one bar for any of the five vowels.
• It is used almost exclusively in katakana; hiragana spells long vowels with vowel kana instead.
• The bar is a full mora of length, not punctuation — dropping it changes the word (ビル "building" vs ビール "beer"; カ vs カー).
• A word can carry multiple bars (スーパー = sūpā).
• In vertical writing, the bar rotates to a vertical stroke.

For the parallel hiragana system, see Long Vowels in Hiragana; for the sound itself, see Long Vowels and Vowel Length.