An adjectival clause is also known as a relative clause. It is a type of dependent clause that functions as an adjective in a sentence. Other synonyms for adjectival clause include relative phrase, adjective phrase, and modifier clause. Adjective clause is another common alternative to the term adjectival clause. These clauses are often introduced by relative pronouns such as who, whom, whose, which, and that. They serve the purpose of providing additional information about a noun or pronoun in a sentence. Adjectival clauses can be either restrictive or nonrestrictive depending on their function in a sentence.