* They introduce prepositional phrases and show relationships between nouns and pronouns.
** Here is a list of prepositions.
It is, at times, okay to end a sentence with a preposition.
EX. What did she sit on?
It is okay to end the sentence with the preposition "on" because without it the sentence does not make sense. You could not say What did she sit?
If the sentence does not change when the preposition is removed, it is better to remove it.
EX. That's where she's at.
If you pull apart the contraction "she's" you get "she is," which can sufficiently end the sentence. "At" is unnecessary.
EX (without preposition). That's where she is.
Prepositions can also be unnecessary within a sentence.
EX. He was pushed off of the edge.
The preposition "of" in the above example is unnecessary. When it is removed, the sentence still makes sense.
EX (without preposition). He was pushed off the edge.