In そうなんですか (sounandesuka) the なん (nan) is used to explain something, give reasoning, or to emphasize something but in これはなんですか (korewanandesuka) the なん is treat as "what", how to know when to use, is it all depends on context?

  • 1
    I'm confused. There is no mention of なに in the question or any of the answers. Is the title supposed to be 何/なん (nan)?
    – istrasci
    Jul 5, 2020 at 18:21
  • It was in the title :).
    – John Adams
    Jul 7, 2020 at 9:27
  • 1
    That's what I mean. You mention it in the title, but nowhere else, and none of the answers do either.
    – istrasci
    Jul 7, 2020 at 16:04

1 Answer 1


Simply, see what comes before なん. If the word before な is something that can take だ/です (a noun, a na-/no-adjective, そう, よう, いつ/だれ/どこ/etc), it means this な is a form of だ and ん is an explanatory-no. See the usage pattern of explanatory-no here.

  • 学生なんですか。 So you're a student?
  • 簡単なんですか。 So it's easy?
  • だれなんですか? Who is it?

If なん is preceded by は or nothing, なん is "what".

  • これはなんですか。 What is this?
  • なんですか。 What (is it)?

EDIT: As broccoli said, は is commonly omitted in casual speech, which makes a sentence like それなんですか technically ambiguous.


  • So it's that one (that we are talking about)!
  • What is that?

But a comma is usually inserted after それ if the latter meaning is intended. Even if there is no comma, you can easily tell the intended meaning from the context.

  • 1
    What about それなんですか? :) Jul 5, 2020 at 15:20
  • So the commas would only be used if は is omitted? If は is not omitted then a commas is not necessary?
    – John Adams
    Jul 6, 2020 at 8:10
  • 1
    @JohnAdams A comma is always unnecessary in Japanese. It's just an arbitrary reading aid.
    – naruto
    Jul 7, 2020 at 6:12

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