Indefinite Article A/An

Indefinite Article A (un/ana) AN (un/una)

 "a/an" before a countable singular noun according to the following rule...

Use "a" before a vowel sound

Use "an" before a consonant sound

                                           a book - a car - a door - a girl - a student - a school

                                       an apple - an egg - an icecream - an orange - an umbrella