I came across the following sentence


translated as

By the way, Lee-kun, why are you busy?

If the の is left out, what's the difference in 'feel' or implication? That is, why is the sentence above different from


From what I've read, の seeks more explanation and context, but for a 'why' question, is an explanation not already expected? What purpose does the の play in the first sentence?

  • Some insight here
    – BJCUAI
    May 17, 2018 at 0:33

2 Answers 2


You can use 「の」 to ask a question in japanese as simply.

For example:


is meaning same as


you also can ask reason with 「なぜ...の」. which is meaning same as 「どうして...んですか」


give a order, very similar to 「しなさい」



の is a nominalizer in this case. Which means that it makes of the followed proposition a noun.

If you know what 「のだ」 is, then you will not have any problem understanding this one, because they are the same の.

どうして忙しい? : Why are you busy?

どうして忙しいの? : Why is it that you're busy?

That is why in some situations and with the right intonation, a question with の may sound a bit girly, because it sounds more pushy than a question without it.

  • I downvoted this but after some further research, I'd like to retract my downvote... but I'm still not sure if this is correct. (see okwave.jp/qa/q3897237.html making the case for and geocities.jp/niwasaburoo/19shuujosi.html seeming to make the case against as far as I can read it)
    – virmaior
    Jul 18, 2018 at 14:53
  • Why would you even downvote without knowing whether it's correct or not in the first place? There isn't 50 type of ending-particle の, the only thing that makes people think there are multiple different の is the different appellation we give to the same thing. Now I can understand the downvote because it's a pretty short answer, but IMO it got the point better than the accepted answer that basically says that いるの? is the same as いますか。 which is only the case semantically. @virmaior Jul 18, 2018 at 18:26
  • I think you're misunderstanding me on multiple fronts here. My initial sense was that this is not correct, but then I doubted my initial sense and checked several resources since it seems like an intriguing interpretation. Some resources agreed, I wanted to retract the downvote. For many sources, nominalization is not the only interpretation and nominalization by itself doesn't make very much sense as to why something is a question.
    – virmaior
    Jul 18, 2018 at 22:05
  • 1
    What the other answer has that yours lacks is that the interpretation of how の works in questions is a shortening of のかい rather than just magically functioning like a question itself...
    – virmaior
    Jul 18, 2018 at 22:07
  • The nominalization in itself has nothing to do with the fact that it's a question. The question was about what the particle adds to a question with this kind of pattern "どうして忙しいの?". I think I answered that pretty well with the example translations I added. @virmaior Jul 18, 2018 at 22:15

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