I would like to know if in the following sentence, special should be plural or not.
The red apples are not special.
I do not feel that this is correct.
This question is too basic; it can be definitively and permanently answered by a single link to a standard internet reference source designed specifically to find that type of information. See the FAQ for guidance on how to improve it.
Adjectives in English are not inflected for number. Special describing a single object remains special when applied to more than one.
None of the adjectives, red, special, English or tasty, differ from a "singular" form.
In English, plural adjectives are not written differently:
If you put an "s" at the end of special, then you're treating it like a noun: