4 Answers

A preposition is a word that shows the relationship between a noun or pronoun and other words in a sentence. 

Example:  A freshman at Harvard University asked an upperclassman, "Sir, Can you please tell me where the library is at?"  The upperclassman, looking unhappy, replied, "At Harvard, we never ever end a sentence with a preposition.  Now, young man, try asking your question again."

The freshman replied, "I beg your pardon, sir, can you please tell me where the library is at, a**hole?"

End of Example: Preposition.

Its a word used with a noun , or pronoun , or method.

A preposition indicates relationship between nouns, pronouns, and other words in a sentence.  Examples are: above, on, after, before, under.  Look at this sentence: The book is on the desk.  ON is a preposition between "book" and "desk".

A preposition tell us the position of something: up, down, on off, of, under, between, underneath, on, amongst

The most common prepositions are "about," "above," "across," "after," "against," "along," "among," "around," "at," "before," "behind.