A preposition is a word that tells you where or when something is in relation to something else. Examples of prepositions include words like 'after', 'before', 'on', 'under', 'inside' and 'outside'.

Yes, you can—most of the time. A preposition shows the relationship of a noun or pronoun to some other word in a sentence. This relationship usually has something to do with time, space, or location.