An is a word that modifies (describes) a verb, an adjective another adverb, or even a whole sentence. Adverbs often end in -ly, but some (such as fast) look exactly the same as their adjective
counterparts​

1. do not confuse theme with a story's subject ending moral 2. which book does the speaker use to illustrate theme? green eggs and ham are you my mother? the cat in the hat 3. theme is usually not stated directly but is instead explicit implied