Use a (NOT an) before a word beginning with a consonant sound
ꭗ He doesn’t own an car. ü He doesn’t own a car.
Use an (NOT a) before a word beginning with a vowel sound
ꭗ She is a excellent teacher. ü She is an excellent teacher.
Use an (NOT a) before words having silent h in front of a vowel
ꭗ The exam lasted about a hour. ü The exam lasted about an hour.
Do not use a or an before Uncountable Nouns
ü He gives great advice. We need also information.