INDEFINITE ARTICLES "A" AND "AN"
Used before:	Therefore:	Such As:	Comic Book Examples:
singular countable nouns (general reference)	Referring to a non-specific object or thing:	Examples such as a superhero, an alien, a gadget	A superhero saved the city.
singular countable nouns (after negation or in questions)	Referring to any one object or thing of a particular kind:	Examples such as a cape, a shield	Do you have a shield like Captain America's?
adjectives	Using before an adjective followed by a noun:	Examples such as a humorous character, a dark city, a powerful villain	The Joker is a humorous character in a dark city.
Remember, "a" and "an" are used for non-specific or general reference, even in comic books! An should always go before words starting with a vowel, and a before words starting with a consonant!!