Determiners are words such as the, my, this, some, twenty, each, any, which are used before nouns. We can also use some determiners as pronouns (i.e. without a noun following and when the meaning is clear without including the noun).
before a noun
as a pronoun (no noun following)
Would you like some bread with your soup?
I’ve got a bar of chocolate here. Would you like some?
We didn’t have enough volunteers to make the project work.
Do you need more paper?
No. I’ve gotenough, thanks.
Several people complained about the slow service.
It’s not just one school that is in financial difficulty; there are several.
Determiners which can be used as pronouns in this way are:
one, two, three, etc.
I’ve had a lot of pairs of sunglasses of different kinds, and I’ve lost a few over the years on various trips.