Why is 'where' an adverb and not a pronoun?

Question

A: Where are you going?
B: I am going to school.

Where took the place of school and something that takes the place of a noun is a pronoun. So, why isn't where a pronoun?

Answer 1

Where does not take the place of school, which is, as you say, a noun.

It takes the place of to school, which is a prepositional phrase acting in this sentence as an adverb of directive location a subject complementing to the verb go.

I am going [to school] → I am going [where] → [Where] are you going?

You may, if you like, consider where as an interrogative pro-adverbPP.

Answer 2

Where is a fronted adverb which is also a wh-word.

Take a look at the following examples:

 1. *You are going New York.

This is ungrammatical. A noun representing a place can't directly follow going. Instead, going can be followed by a prepositional phrase or an adverb:

 2. You are going to New York. (preposition phrase--okay)

 3. You are going quickly. (adverb--okay)

So what do we have in the following example?

 4. You are going there.

It looks like an adverb to me. There's no preposition, so it can't be a preposition phrase, and it's not a noun because we established (with example 1) that a noun would be ungrammatical.

Now let's replace there with where:

 5. You are going where?

It still looks like an adverb to me. We've established that a noun doesn't work in this position, so where isn't taking the place of a noun. That means it can't be a pronoun.

Of course, example 5 is only allowed in limited circumstances. Two examples are reclamatory questions, in which you're asking someone to repeat themselves, and incredulity questions, where you're expressing disbelief about what someone just said. They also feature in situations that involve sustained questioning, such as in court or on a game show. But outside those limited circumstances, where needs to be fronted, which means moving it to the front of the sentence:

 6. *Where you are going? (ungrammatical; you and are must be inverted)
 7. Where are you going? (okay)

In 6, the wh-word is fronted; this is ungrammatical without subject-auxiliary inversion. In 7, the subject and auxiliary are inverted, so it's grammatical again.

So it seems to me that the wh-word in this case is also a fronted adverb.

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In this answer, the * symbol means I've identified the sentence as ungrammatical.

Answer 3

Well this is indeed a difficult question, but really interesting.

So,

First off, the question Where are you going doesn't always mean to school. Cause usually people don't know (yet) the answers to their questions. It could be to work, to that building, to nowhere, or even I don't know. So that doesn't make the where replace exactly the school.

If the where is a pronoun:

True, a pronoun replaces a noun and its "form" is of that noun. Cause its function is to substitute the noun. By extension, a pronoun and the noun it replaces are interchangeable.

You do understand, that where in that interrogative sentence cannot be replaced by to school: to school, are you going?. Plus, you cannot say that a positive sentence replaces some interrogative one. Even, in a positive sentence, where still cannot function as replacement (pronoun).

Replacing is something like this:

I know the place.

--> I know that.

While where acts like this (as an adverb):

I know the place.

--> I know the place (where) you went. (where qualifies the word place)

When the where is an adverb:

Now, it makes more sense when you're calling the where an adverb. Here, an adverb, essentially, is a word that changes or qualifies the meaning of a verb, adjective, other adverb, clause, sentence or any other word or phrase.

So if my deduction is correct, the where there functions to qualify the "original" question (sentence) are you going?. Similarly, the rule works for the examples I wrote above. More examples to ensure you:

did you go yesterday?

where did you go yesterday?

did you teach English?

where did you teach English?

Answer 4

“Where” is usually an adverb, but in some cases, it can be pronoun. When “where” is the object of a preposition, it is a pronoun. For instance, in the question,

“Where are you from?”

which can be reordered as

“From where are you?”

“where” is the object of the preposition “from”. An answer to that question could be,

“I am from the United States.”

“the United States” takes the place of “where”, which makes it a pronoun. However, in your sentence, “Where are you going?”, to which a possible answer could be, “I am going to school,” the entire prepositional phrase “to school” takes the place of “where”, and “to school” is an adverbial phrase modifying the verb “am going”. This makes “where” and adverb instead of a pronoun. So yes, “where” can be a pronoun, but usually when it is the object of a preposition. Otherwise, it is most likely an adverb.