A prepositional phrase always begins with a preposition. The last word in a prepositional phrase is a noun. That noun is called the object of the preposition.
Look at these prepositional phrases. In each phrase, the first word is a preposition. The last word is a noun. We label that noun object of the preposition.
under the sofa
behind the door
in the bucket
over the rainbow
after the game
before the movie
up the staircase
None of these phrases is a complete thought. A prepositional phrase is only part of a sentence.
A prepositional phrase in a sentence looks like this: My cat ran up the staircase.
Every prepositional phrase begins with a preposition and ends with the object of the preposition.
It’s your turn. Find the prepositional phrase in this sentence. Then label the object of the preposition. I dropped my fork under the table. Did you figure it out? Good for you!