When to Use the Indefinite Article "An" In English we want add an "n" to the article when it is in front of a word that starts with a vowel sound. For example: "An amazing shot" Vowel A "An elephant" Vowel E "An isosceles triangle" Vowel I "An open court" Vowel O The long u sound /you/ is an exception: For example: "A unicycle" "a uniform" "a unique rule." Words that start with the short "u" sound DO pair with the article "an": for example: "an underbelly" "an ugly picture"