The indefinite article takes two forms. It’s the word a when it precedes a noun that begins with a consonant. It’s an when it precedes a noun that begins with a vowel. The indefinite article indicates that a noun doesn’t refer to a particular thing. For example, you might ask your friend, “Should I bring a gift to the party?” Your friend will understand that you are not asking about a specific type of gift or a specific item. “I am going to bring an apple pie,” your friend tells you. Again, the indefinite article indicates that she is not talking about a specific apple pie. Your friend probably doesn’t even have any pie yet. The indefinite article only appears with singular nouns.