What word can be used as an adjective and a pronoun?

The most common are the possessive pronouns and possessive adjective forms of personal pronouns.

The difference is that a possessive pronoun takes the place of a noun, showing that something belongs to that person or thing. The possessive pronouns are mine, yours, his, hers, its ours, theirs.

For example: The house on the corner is ours.

Possessive adjectives describe a noun. A possessive adjective is placed just before the noun that it describes. The possessive adjectives are my, our, your, his, her, its.

For example: Our house is on the corner.

Then there are the demonstrative pronouns (this, that, these, those). Again, the pronouns take the place of a noun in a sentence:

That is my favorite.

The adjective describes the noun and is placed just before the noun it describes:

That movie is my favorite.

The indefinite pronouns can also either take the place of a noun or describe a noun; for example:

Pronoun: You may have some, we have more in the kitchen.

Adjective: Please have more noodles, they're good with some gravy.