a) The car is red.
An adjective gives information about a noun. In the examples the adjectives tells us about the quality, the appearance or the speakers ideas about the subject nouns.
Note that the subject in example a,b,c and d are the same, but the adjectives are different. Therefore, each adjective modifies the noun in a different way as: size, color, appearance and opinion.
Adjectives can also modify pronouns as in examples f, g, and h.
i) They are happy
A & an can not be used with a single adjective
Adjectives don’t have plural forms: