The Internal Structure of Adjective Phrases in English Reference Sheet Adverb Phrase Adverb phrases are phrases with an adverb functioning as the head of the phrase plus any other adverbs functioning as adverb phrase modifiers and perform the grammatical function of adjective phrase modifier within adjective phrases. Adverb Phrase | Adjective very | smart Prepositional Phrase Prepositions are traditionally defined as "words that indicate relationships between nouns, adjectives, and verbs and other nouns, adjectives, and verbs." Prepositional phrases perform the grammatical functions of adjective phrase modifier and adjective phrase complement within adjective phrases. Adjective | Prepositional Phrase fond | of pumpkin cookies Verb Phrase Verbs are traditionally defined as "words that express an action or state" and perform the grammatical function of adjective phrase complement within adjective phrases. Adjective | Verb Phrase glad | to help Noun Clause Noun clauses are subordinate clauses that perform the grammatical function of adjective phrase complement within adjective phrases. Noun | Noun Clause afraid | that the potato salad is rancid