Answer: a noun or a pronoun.
Explanation: an adjective is a word that describes or modify a noun or a pronoun. There are many different types of adjectives, for example: descriptive adjectives (such as: intelligent, kind, good, bad, green, etc), demonstrative adjectives (this, that, these, those), quantitative adjectives (one, two, many, whole, etc), possessive adjectives (mine, yours, ours, theirs, etc), interrogative adjectives (which, what, whose), etc.