Interrogative Adjectives
An interrogative adjective ("which" or "what") is like an interrogative pronoun, except that it modifies a noun or noun phrase rather than standing on its own (see also demonstrative adjectives and possessive adjectives):
Which plants should be watered twice a week?
Like other adjectives, "which" can be used to modify a noun or a noun phrase. In this example, "which" modifies "plants" and the noun phrase "which plants" is the subject of the compound verb "should be watered":
What book are you reading?
In this sentence, "what" modifies "book" and the noun phrase "what book" is the direct object of the compound verb "are reading."
Indefinite Adjectives
An indefinite adjective is similar to an indefinite pronoun, except that it modifies a noun, pronoun, or noun phrase, as in the following sentences:
Many people believe that corporations are under-taxed.
The indefinite adjective "many" modifies the noun "people" and the noun phrase "many people" is the subject of the sentence.
I will send you any mail that arrives after you have moved to Sudbury.
The indefinite adjective "any" modifies the noun "mail" and the noun phrase "any mail" is the direct object of the compound verb "will send."
They found a few goldfish floating belly up in the swan pound.
In this example the indefinite adjective modifies the noun "goldfish" and the noun phrase is the direct object of the verb "found":
The title of Kelly s favourite game is "All dogs go to heaven."
Here the indefinite pronoun "all" modifies "dogs" and the full title is a subject complement.