Here's why:
* No subject and verb: Prepositional phrases are groups of words that start with a preposition (like "in," "on," "at," "with," "to," "from," etc.) and end with a noun or pronoun (the object of the preposition). They do not have their own subject performing an action (verb).
* Adverbial function: Prepositional phrases often function as adverbs, modifying verbs, adjectives, or other adverbs. They answer questions like "where?", "when?", "how?", or "to what extent?".
Examples:
* "The cat slept *on the couch*." ("on the couch" tells us where the cat slept - modifies the verb "slept")
* "She walked *with confidence*." ("with confidence" tells us how she walked - modifies the verb "walked")
* "The house *across the street* is very old." ("across the street" tells us where the house is - modifies the noun "house")
Let me know if you'd like more examples or want to explore other types of phrases!