Adjective-No in a Question format?


I'm having a difficult time understanding the use of の-Adj in the JLPT N5
grammar examples and practice I've been studying and haven't found a good
resource for finding the answer. The sentence is fairly simple but I can't
tell what the purpose of the の at the end of the Adj is in it. It goes:

> 大きいのは いくらですか。 Ookii-no wa ikura desuka?

Does anybody have any clue? Thank you!




の in this case is a pronoun that can be translated to English as "one".

(More precisely, it's a "dependent indefinite pronoun")

Therefore:

> 大きい = "big" (adjective)
>
> 大きいの = "big one" (noun equivalent)

By applying this translation, we can see the problem that happens if we don't
use の:

> *大きいはいくらですか = "how much is the big" (wrong)
>
> 大きいのはいくらですか = "how much is the big one" (correct)

For more research on uses of の, I recommend reading the relevant chapters of
the book "A Dictionary of Basic Japanese Grammar".

