Articles an/a
par Miguel Gonzalez
1. A
1.1. Used only in singular nouns
1.1.1. a pencil
1.1.2. a book
1.1.3. a clock
1.1.4. a TV
2. An
2.1. Used with words that start with a vowel sound
2.1.1. an star
2.1.2. an house
2.1.3. an wallet
2.1.4. an door