Usage of か after a clause?


Here's a sentence I found:

> デパートはどこにあるか、知っていますか？  
>  Do you know where the department store is?

What's the purpose of the か particle in 「どこにあるか」? Under what circumstances do
I use it?

I'm fairly sure it's not the か that's normally used to form questions, like
the second か in that sentence, nor is it the か that means “or.”




These are sometimes called **embedded questions** , but if you look them up
you'll find a variety of terminology in use, including "embedded interrogative
content clauses" and "indirect questions".

* * *

I think the か in embedded questions is more or less the same か used to form
regular questions. But there are a couple differences:

  * In an embedded question, it's okay to have だ before か:

> _1._ [ 誰 **だか** ] 分からない ← _okay_

  * In an embedded question, か generally can't be omitted:

> _2._ デパートは [ どこにある **か** ] 知っていますか？ ← **か** _can't be omitted_

Another difference is that embedded interrogatives can function like nouns
(for examples, see Satoshi Tomioka's paper [_Japanese Embedded Questions are
Nominal_](http://udel.edu/~stomioka/papers/tomioka_QVE.pdf), especially pages
8 and 9). In fact, we might want to say as a matter of theory that the
か-phrase is the direct object of 知る:

[code]

    　 　 _3a._　[　どこにあるか　]- **を**　知らない  
    　 　 _3b._　[　どこにあるか　] ****　知らない
[/code]

We might choose to say that sentence 3b is derived from sentence 3a by
omitting を. But in practice, it's usually omitted, particularly in
conversation, and sometimes inserting を is strange, so I'm not sure if this is
the right approach. ([See our discussion in
chat.](http://chat.stackexchange.com/transcript/message/18356802#18356802))

* * *

We have embedded questions in English, too:

> _4a._ **What** are you talking about?  
>  _4b._ I don't know [ **what** you're talking about ].

In _4a_ we have a basic question, and in _4b_ we have the embedded question
corresponding to _4a_. Likewise, in Japanese, we can write:

> _5a._ **何** を言っているのか？  
>  _5b._ [ **何** を言っているのか ] 分からない。

As you can see, embedded questions straightforwardly correspond to main clause
questions, although in each language there are small differences in syntax.

