grammar - About the sentence structure "Do you see where the sign is?

This is from a textbook for ESL students.

At the information desk, a lady asks, "Where is the restroom?" A man says, "It's just behind you. Do you see where the sign is?"

Is this sentence structure "Do you see where the sign is?" the same as, for example,

"Do you know where the restroom is?"

If I take this sentence as a relative clause, does it work?

Answer

Let's form a question. We'll perform four basic steps.

1. 
   

   First, let's start with a declarative clause:

   
   

   
   

   The restroom is here.

   
   

   
   


2. 
   

   Next, let's turn it into an interrogative clause. We'll do this by putting the interrogative word where in, replacing here:

   
   
   

   
   

   The restroom is where?

   
   

   
   


3. 
   

   Next, we need to move the interrogative phrase containing where to the front. In this example, that phrase is just the word where by itself:

   
   

   
   

   [ where the restroom is ]

   
   

   
   



4. 
   

   And finally, we'll make it into a main clause question using Subject-Auxiliary Inversion. Our subject is the restroom, and our auxiliary is is, so we'll just switch those two around:

   
   

   
   

   Where is the restroom?

   
   

   
   

And we're done! Those are the basic steps. They can be a little bit different for other sentences, and I've written up some more examples over here, but for this question we're going to ignore those details and move on. We've got ourselves a question!

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Not every interrogative clause is an entire sentence by itself. Sometimes we use an interrogative clause as part of a larger sentence. When we do, we follow the same steps, except we don't perform Subject-Auxiliary Inversion. Let's take a look:

1. 
   

   We'll start with our interrogative clause from step 3 above:

   
   

   
   

   [ where the restroom is ]

   
   

   
   


2. 
   

   We can use this as part of a larger sentence as a content clause:

   
   
   

   
   

   I don't know [ where the restroom is ] .

   
   

   
   


3. 
   

   And that larger sentence can be a question, too:

   
   

   
   

   Do you know [ where the restroom is ] ?

   
   

   
   



4. 
   

   And we can use your other example the same way, because it has the same structure:

   
   

   
   

   Do you see [ where the sign is ] ?

   
   

   
   

Okay, let's move on!

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Subordinate clauses can be relative, but not all of them are. The name for a basic type of subordinate clause without any special function (relative or comparative) is "content clause", and that's the name I've used so far.

But you could use a clause like this as a relative if you wanted to. For example:

I went to the school [ where the sign is ] .

Here, "where the sign is" is a relative clause modifying the head noun "school". But there's no such relationship in the other examples, so we have no reason to call them relative clauses. That's why I used the term "content clause" instead earlier.

In short, your examples have the same structure as one other, but they're not relatives. They're interrogative content clauses.