An adjective clause is a clause that modifies a noun or pronoun. Like other clauses, an adjective clause can be made up of a subject and a verb. It can also contain relative pronouns like “that” or “which,” as well as other descriptive words. Adjective clauses can be used to describe whole nouns, or they can be used to replace the noun with a pronoun. For example, “The cat, which was very small and cute, belonged to my little sister.” In this sentence, “which was very small and cute” is an adjective clause that describes the cat.