The indefinite articles A and an

1. We do not use a / an with names or nouns that are written in plural or are uncountable, because a / an means "one"

1.1. My grand parents are teachers (not...a teachers)

2. The an article is used for nouns or nouns that begin with a vowel

2.1. an actor

2.2. an hour

3. The article a is used for nouns or nouns that begin with consonants.

3.1. arose

3.2. a house

4. We use a / an with a name or noun to talk about a member of a class

4.1. Lee is a chinese name

4.2. A kid phoned this morning

5. We use a / an when we describe people or things.

5.1. My girlfriend is a beautiful woman

5.1.1. Schedule

5.1.2. Budget