Adjective without noun (i.e. I like the red [one])

Question

A non native speaker asked me this but I'm unsure.

Is a sentence like this correct:

"She liked the red ball; I liked the blue."

Replace blue with literally any adjective.

I'm unsure if this only works with "certain" adjectives that can be read as nouns "The Poor" "The Hungry".

"She liked fast birds; I liked slow."

There - that one there is no "the" construction even. I think in some sentences, particularly with "the" in front of the hanging adjective -- it reads as correct but maybe technically isn't?

Answer 1

[1] She liked the red ball; I liked the blue (one).

[2] She liked fast birds; I liked slow (ones).

Without "one / ones", these consist of a 'fused-head' construction, where the head is combined, or 'fused', with a dependent element, either a determiner or, as here, a modifier. That is, a single word is at the same time a determiner or a modifier and also the head.

Here the fusion is between head and modifier. In both examples an adjective serves as modifier and as head at the same time. In [1] we understand "blue" to mean "blue ball", and in [2] "slow" to mean "slow birds".

By contrast, if the common noun "one(s)" is added there is no fusion of head and modifier. Instead, "one" and "ones" are pro-forms with "ball" and "birds" as antecedent.

Answer 2

Yes. You can use an adjective with one[s], or alone, when it's contrasted with (noun + different adjective).