Indefinite article

"an" is an indefinite article in English, used in contrast to the definite article "the". It comes before a noun and indicates an unspecified meaning for a singular noun. Also, when the first sound of a noun is a vowel sound, "an" is used as the indefinite article instead of "a". For example, "an apple" or "an hour".

Example

1. I need an umbrella because it's raining outside.
2. Can you please give me an apple from the fruit basket?
3. She bought an expensive dress for the wedding.