Down

TakaThen what part of speech is "down"? An appositive noun? Or an adverb? Or is it something else?

It could be any of three things:

a) as an adjective in the post-modifier position: "the down direction"
b) as an adverb: the direction down (eg. to the basement)
c) as a noun: object complement (a specification of the kind of direction)

Related to that question, just out of curiosity, let me ask, AS.

Do you think "there"s below are adverbs?

Boys there want to see you.
Take that book there.

TakaTake that book there.

Ambiguous:
a) Adverb: that that book to that place (there).
b) Adjective, post modifier, specifying which book you are talking about.
Note the substandard variant: "Take that there book"

TakaBoys there want to see you.

The boys over there want to see you. (The boys in that pl

The reason I asked the question about "there" was that as you pointed out, "The boys there" is the same as "The boys in that place" and if you took such "there" as an adverb, I thought it was the reason that you took the down in question as an adverb (i.e the direction to X?the direction down).

I'm still kind of having a little difficulty understanding your b)

TakaDo you mean it's an ellipsis of "the direction down to X" or something?

It could be an interpretation

The visitor asked where the subway was, so I indicated the direction (to go) down.

I see.

To conclude the discussion, let me confirm.

Your first choice, without further context, it's b). But a), b), and c) are all natural and possible, right?