Prepositions are never adverbs or adjectives. However, nouns can be adjectives and sometimes verb. Prepositions show direction. They are words like under, around, beneath, over, inside, on, up, etc. Also included are the "f" words like of, if, from, for; FANBOYS is a way to remember the commonly used prepositions-for, and,nor,but, or, yet, and so.