Prepositions can have <u>three purposes </u>in a sentence. They can act as an adjective, and <em>modify a noun</em>, they can act as an adverb, and <em>modify a verb</em>, or as a nominal when used in <u>conjunction with the verb form to be</u>. Remember to avoid using prepositions at the end of a sentence, because prepositions <em>must be followed by a noun</em>, and have an object.
