Demonstrative Adjectives

The demonstrative adjectives "this," "these," "that," "those," and "what" are identical to the demonstrative pronouns, but are used as adjectives to modify nouns or noun phrases, as in the following sentences:

I want to buy that jacket over there

In this sentence, the demonstrative adjective "that" modifies the noun "jacket" and the noun phrase "that jacket" is the object of the sentence and "over there"shows us that jacket is far.

 This pencil is yours.Here you are!

Here "this" modifies "pencil" and the noun phrase "this pencil" is the subject of the sentence.

Even though my friend preferred those plates, I bought these.

In the subordinate clause, "those" modifies "plates" and the noun phrase "those plates" is the object of the verb "preferred." In theindependent clause, "these" is the direct object of the verb "bought."
Note that the relationship between a demonstrative adjective and a demonstrative pronoun is similar to the relationship between a possessive adjective and a possessive pronoun, or to that between a interrogative adjective and an interrogative pronoun.