Undefined articles A and an

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

1.1. Carla lives in a nice big house

1.2. My uncle is an engineer

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

2.1. She is a doctor

2.2. My girlfriend is a beautiful woman

2.3. That is an elephant

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

3.1. a crab

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

4.1. a cat

4.2. a chair

5. https://www.youtube.com/watch?v=hg9FcAz7-ag