OO and OU to extend the Oh sound?

I have just started to learn Japanese. From other sources I learned that to extend the Oh sound you write OU. However, in some vocabulary, such as big, the extended Oh sound is written OO. I get this vocabulary marked wrong often because I write OU for the extended Oh sound. Furthermore, with other words the Oh sound is extended with OU. Why the difference?!

Isn’t it that it’s OU for on’yomi and OO for kun’yomi? :thinking:

You usually use kun’yomi for words with hiragana attached to them, like 大きい, and on’yomi for words with only kanji, like 大王 (だいおう).

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It just depends on the word. Also when you have katakana that are written with the vowel extender ー, it’s hard to say whether it’s an お or a う, so how it then gets written in romaji could be as a doubled-vowel or as a dash.

For instance コーヒー (coffee) is typed こーひー, but is it koohii or kouhii? Usually people type it as koohii in romaji, but I’ve seen things like ko-hii, kōhii and kōhī before too.

All that really matters is that the vowel sound is extended, and that you do know how to correctly write the words. For instance the general counter for 10 things is とお, never とう.

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You’re right: What’s most important is that I do know when the Oh is elongated. It drives me crazy that I continually get words wrong by not using the correct form. Anyways, thanks for letting me know.

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It’s just a spelling convention from etymology. As noted, おお spellings come from older Japanese words. The classical spelling was おほ, but it was updated to おお go represent the fact that that’s how it sounds.

おう spellings come from Chinese, and the classical spelling was わう, but again, got updated to おう to reflect the change.

In modern Japanese pronunciation おお and おう sound the same if there is no “morpheme barrier” between the characters, so they both sound like a long o sound. That is to say, something like the verb 追う (おう) is different because the お and the う are different morphemes, and so you can hear them individually.


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