How do you find the prepositional phrase in sentence forget to put a stamp on envelope?

The prepositional phrase in the sentence "Forget to put a stamp on the envelope" is "on the envelope".

Here's why:

* Preposition: The word "on" is a preposition, indicating the location or position of something.

* Object of the Preposition: The phrase "the envelope" follows the preposition "on" and acts as the object of the preposition.

* Complete Phrase: Together, "on" and "the envelope" form a prepositional phrase, modifying the verb "put".

The prepositional phrase tells us where the stamp is being placed.