The Katakana Long Vowel Mark ー: When and How to Use It
In hiragana you stretch a vowel by adding あ・い・う・え・お. In katakana you do something completely different — you use a single dash, ー. Learners rarely get told this clearly, so they leave it out and write コヒー instead of コーヒー. Here is the rule.
What the ー Mark Is
The mark ー is called the chōonpu (長音符) — the “long-sound mark.” It means “hold the previous vowel for one more beat.” So コーヒー is ko + (hold) + hī, four beats: ko-o-hi-i.
Written sideways (horizontal text) it is a horizontal dash; in vertical text it becomes a vertical line. Either way, it does the same job.
The Rule: ー for (Almost All) Katakana Long Vowels
Because katakana is used for loanwords, and loanwords are full of long vowels, you will see ー constantly. The rule is simple: in katakana, lengthen any vowel with ー — never with あいうえお.
One catch: which syllables are long in a loanword is often unpredictable, because it follows the original foreign pronunciation, not a Japanese rule. You simply learn each word — but the mark is always ー.
Examples
Common Mistakes
- Leaving the ー out: コヒー ✗ instead of コーヒー ✓ — this changes the word’s length and can make it hard to understand.
- Using a hiragana-style vowel: コーヒイ ✗ — katakana never lengthens with イ here; use ー.
- Forgetting ー in your own name or city when written in katakana, if it has a long vowel.
Teacher’s Note
The ー mark is also used in casual hiragana for a stretched, expressive sound — すごーい, ながーい — but in standard writing, ー belongs to katakana. When you read a katakana word aloud, give the ー its full beat; that single beat is often what makes a loanword sound natural.
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