Articles a/an

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

1.1. EXAMPLE

1.1.1. AN Apple

1.1.2. An elephant

1.1.3. An Iguana

1.1.4. An Umbrella

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

2.1. EXAMPLE

2.1.1. A cat

2.1.2. A Banana

2.1.3. A pig

2.1.4. A Puppy

3. 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

3.1. He is an excellent teacher.

3.1.1. Essay exam

3.1.2. Oral exam

3.1.3. Multiple choice

3.2. I saw a really beautiful eagle 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