Question: お or う after o-vowel

Hi guys,

This is just a question after I keep making the same mistakes during my reviews. As I understand, the お- or う- character is sometimes placed after an o-vowel to make a long vowel.

とおか - Too-ka - Ten Days
ようか - Yoo-ka - Eight days.

I often make the mistake by writing a word with お where it should have been う and vice versa. So I was wondering if there was some system to all this, which could help me in my learning.

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Usually it’s う, sometimes it’s お; remember when it’s お and assume う in other cases.


Basically, the reason for this difference is etymology. The Japanese government did a big overhaul of kana usage after the second world war so that the way things things were written was more in line with how they were pronounced. Long “o” sounds that were previously written as ~おほ or ~おを were both standardised to be written as ~おお, while long “o” sounds written as ~おふ became ~おう. The latter is much more common than the former, though, so as Kumirei said, just remember the specific odd ones.

They’re pronounced the same (unless the ~お and the う come from different kanji, in which case it was never a long “o” sound in the first place).


Alright thanks @Belthazar and @Kumirei for your kind explanations.

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う is much more common, so it’s usually safe to assume this as the default. When a word uses the exception of お, I use my own mnemonic that this new word is extra special and therefore “honorable” because it’s like adding an お honorific at the beginning of a word. Also お is shaped like a cross so I use that as further reinforcement that the word must be honoring God or something

Thanks, that sounds useful, I will try that!

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