This document discusses prepositions and their usage. It defines a preposition as a part of speech that connects a noun or pronoun to another word and cannot stand alone. It then lists common prepositions like above, after, among, and provides examples of how they are used to indicate relationships of time, direction, location, manner and quantity. The document also gives examples of preposition usage in sentences and clarifies the specific uses of some prepositions like on, in, at.