A / AN (Indefinite Article)

Students struggle with this on a regular basis so it is necessary for them to have a lot of practice.

1. A is used with singular countable nouns that begin with a consonant.

• He is a teacher.
• She doesn't own a car.
• There is a bear at the zoo. 

2. An is used with singular countable nouns that begin with a vowel.

• He is an actor.
• She didn't get an invitation.
• There is an eagle at the zoo.

Using a or an depends on the sound that begins the next word. 

• a + singular noun beginning with a consonant sound: a user (sounds like 'yoo-zer,' i.e. begins with a consonant 'y' sound, so 'a' is used); a university; a unicycle
• an + nouns starting with silent "h": an hour

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

• There is a bears in Yellowstone National Park. Not Correct
• There are bears in Yellowstone National Park. Correct

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.

• He is an excellent teacher.
• There is a bautiful dog in the garden.
• There is a green apple in the fridge.
• There are fresh plums in the cupboard.