During my studies I stumbled on this sentence : 彼女はそれがいくらなのかわかります 

I am having some trouble understanding why you would need to use "なの” in this context.

I think I understand the basics using of のです / なのです to give the sentence an explanatory meaning, but why here ?

If we want to say : "She knows how much this costs"

Can we not just say : "彼女はそれがいくらかわかります” ? Why would we have to add なの after いくら ?


Let's just consider the inner fragment


How would you parse this? Is it a sentence? If it is a sentence, where is the verb?

The grammar with わかる is generally it takes a sentence followed by か to indicate what is understood.


parses much like the English (only it potentially sounds a lot ruder in Japanese).

That, how much?

This phrase needs a verb. In formal speech, you might ask


But generally you don't keep the formal verb in an embedded sentence. So, we need to change this to an informal sentence.

You might guess


But that just doesn't work. Instead you can opt for one of the following two:



The first of this sounds extremely literary. If you talk this way you'll sound like someone in parliament making a speech: rather pompous.

In the second one, the な is だ transformed for use in an embedded structure. I'm not sure quite how to explain the の but, if you're going to transform a formal sentence ending in ですか, then

ですか ==> なのか

So, in summary, 彼女はそれがいくらかわかります would be ungrammatical.

  • Thank you for the explanation ! That is about what i had gather : the の is really confusing to me because it sounded like it was nominalizing "それがいくらです” and I did not really understand why. So I just have to remember that in that case the ですか becomes なのか。 Does that mean merely saying "彼女はそれがいくらかわかります” without the "なの” would also have been wrong? Thanks so much for the help !
    – Wignam
    Apr 10 at 16:18

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