Articles A, AN

1. The article AN is used before singular, countable nouns which begin with vowel sounds.

1.1. He is an actor.

1.2. She didn't get an invitation.

1.3. I saw an eagle at the zoo.

2. If there is an adjective or an adverb-adjective combination before the noun, A(AN) should agree with the first sound in the adjective or the adverb-adjective combination.

2.1. He is an excellent teacher.

2.2. I saw a really beautiful eagle at the zoo.

3. The article A is used before singular, countable nouns which begin with consonant sounds.

3.1. He is a teacher.

3.2. She doesn't own a car.

3.3. I saw a bear at the zoo.

4. Remember that A(AN) means "one" or "a single". You cannot use A(AN) with plural nouns.

4.1. I saw a bears in Yellowstone National Park. Not Correct

4.2. I saw bears in Yellowstone National Park. Correct