A noun phrase refers to a group of words that functions as a noun, including the noun and any modifiers or determiners. Modifiers such as adjectives, prepositional phrases, and relative clauses provide additional information about the noun. Determiners like articles and possessives also clarify or describe the noun. Similarly, an adjective phrase is a group of words that describes a noun or pronoun, consisting of an adjective and any additional modifiers. Both noun phrases and adjective phrases add detail to nouns or pronouns in a sentence.