Indefinite Article ( a / an )

1. Use "an" if the word starts with a vowel.

1.1. Example

1.1.1. an apple

1.1.2. an umbrella

1.1.3. an eraser

2. Use "a" if the word starts with consonant.

2.1. Example

2.1.1. a girl

2.1.2. a cat

2.1.3. a bird

3. Don´t use a/an to identify uncontable nouns. For example: Sugar, Milk, Salt, Wine, etc.