Find the prepositional phrase in a sentence by locating the preposition or an adverb. Adverbs describe verbs (quickly, heartily, mildly). A preposition gives information about a noun, its location or relationship to the rest of the phrase (between, upon, near, with).
Read the group of words that begins with the adverb or preposition to determine if it describes the noun. If the phrase describes the object of the preposition (the noun or pronoun), it is an adjective phrase. For example, in the sentence, "That house on the east side of the city is for sale," "on the east side of the city" is the adjective phrase that describes "that house" ("on" is the preposition).
Differentiate an adjective phrase from an adverbial phrase by what the phrase says and its construction. If the phrase modifies or describes a verb, an adverb or an adjective, it is an adverbial phrase. For example, in the sentence, "The girls arrived early in the morning," "in the morning" is an adverbial phrase because it modifies the adverb "early."