Prepositional phrases can function as both adjectives and adverbs.
Here's a breakdown:
* Adjective: A prepositional phrase modifies a noun or pronoun, answering the questions "which one?" "what kind?" or "how many?"
* Example: "The book on the table is mine." ("on the table" modifies the noun "book")
* Adverb: A prepositional phrase modifies a verb, adjective, or another adverb, answering questions like "how?" "when?" "where?" "to what extent?" etc.
* Example: "He walked to the store." ("to the store" modifies the verb "walked")
It's important to remember that a prepositional phrase is a group of words beginning with a preposition and ending with a noun or pronoun (the object of the preposition).