One of the prevalent questions on the English Language and Usage – Stack Exchange is about whether a or an is the correct indefinite article to use. It’s a straightforward question, but like all questions, there are subtleties that raise further questions.
General Rule
The question of “a” vs “an” is always decided by the pronunciation of the word that follows the article, without exception. Words that begin with a vowel sound, such as apple, egg, or owl, use the indefinite article an. …