When to use う?

Hi all!

I’m struggling to understand when I’m to use う. I make more mistakes on this point than on any other, with the similar application of お coming in second place.


戸 vs. 刀

休日 vs. 今日

八日 vs. 四日

Is there a rule that I should be aware of? Or is this something one needs to simply memorize in each instance?

Many thanks in advance for your kind guidance!


It’s pure memorization as far as I know.


You’ll see it all the time. You just have to learn it. It can be frustrating.


Every Japanese person I have talked to about this sort of thing say its just something you know, theres no real rule to follow. Just memorize it and call it a day.


Yeah, there’s really no rule in any of the examples you’ve mentioned beyond “well, that’s just how the word is pronounced”.

An English equivalent to your examples might be "I’m having trouble remembering the difference between ‘tree’ and ‘three’ ", and really the only thing I could say to that is “they’re simply different words”.


The only thing I’d like to add to what’s been stated is that there are no silly questions.

It’s good to ask if you’re confused about something. In this case, rote memorization really is the only way.

Westerners tend to have problems remembering:

  • broad vowels (と•とう and おばさん•おばあさん — four completely different words that are sometimes difficult for western ears to differentiate).

  • when and when not to use the small tsu (げつようび but みっか)

  • rendaku (いけばな not いけはな)

There are patterns to some of these, but there are exceptions, too. The good news is that the human brain is incredibly well adapted to recognizing patterns: with enough repetitions you will start to recognize things on your own, and the exceptions to a “rule” will stand out all the more.