Remlori › Japanese › Guides › Japanese long vowels: おう, おお and the ー mark

Japanese long vowels: おう, おお and the ー mark

A long vowel lasts about two beats. In ordinary pronunciation, おう often represents a long o, rather than a quick o followed by an English-style oo.

Keep the extra beat

Compare おばさん (obasan, aunt) with おばあさん (obāsan, grandmother). The second word has an extra a beat. Practise slowly by tapping o / ba / a / sa / n; then keep the same timing when you say it smoothly.

Common spellings

がっこう (gakkō) — school: おう writes the long o
おおきい (ōkii) — big: おお writes the long o, and いい is long too
せんせい (sensei) — teacher: えい is commonly pronounced with a long e
コーヒー (kōhī) — coffee: each ー extends the vowel before it

Spelling and pronunciation are different jobs

Romanization may show kō, kou or koo for different writing conventions. Use the Japanese spelling to learn how the word is written and the audio to learn its sound. Do not rewrite おう as おお simply because they can sound alike.

Not every neighbouring pair of vowels merges. Word structure matters, so treating every ei or ou as a mechanical instruction will eventually mislead you. Learn these common patterns with whole-word audio.

Try it before looking

In コーヒー, which vowels become long?
What distinguishes おばさん from おばあさん?
Does hearing a long o tell you whether to write おう or おお?

Show answers and reasons

Both o and i: kōhī.
The length of a; keep its extra beat.
No. Learn the spelling of the word.

Compare this with small っ, which lengthens a consonant.

Listen and repeat

Play an example, repeat it, then cover its reading and try again.

おおきい
せんせい

Keep practising

Listen to the hiragana chart and practise words with pictures. Read a short example, cover the reading, then say it again from the script.

Reference: The Japan Foundation: Irodori. Explanations and practice here are written by Remlori.

Practise sounds, words and sentence building in the free first chapter.

Start Japanese Lesson 1

Check the extra beat

Choose a mode and a group. Each round has up to ten questions. Wrong answers go into a retry round.

Try these questions, then open the answers. The interactive version needs JavaScript.

Which spelling has the extra a beat?
Answer and explanation
おばあさん — おばあさん has a long a.
What does the first ー extend in コーヒー?
Answer and explanation
o — The first ー follows コ and extends its o vowel.
What does the second ー extend in コーヒー?
Answer and explanation
i — The second ー follows ヒ and extends its i vowel.
Does a long o alone tell you to write おう rather than おお?
Answer and explanation
No — Learn each word’s spelling; both patterns can represent a long o.
How many beats does きょう have?
Answer and explanation
2 — きょ is one combined beat, followed by a long-vowel beat.
What is lengthened by small っ?
Answer and explanation
A consonant — Small っ adds consonant timing. A long vowel extends a vowel.