A or An - The Indefinite Articles
The difference of a and an
You can use a and an for all genders in the singular. If you have to use a or an, depends on the sound the word begins with.
If the first sound is a consonant you have to use a.
If the first sound is a vowel you have to use an.
an ice cream
an hour - because the first letter is silent and the word starts with an au-sound.
a uniform, a university - because the first letter starts with a ju-sound.
Use of the indefinite article a and an
1. We can use a and an before countable nouns:
That's a fast car. My aunt has got a big house.
2. We often use a and an to tell what someone/something is and what someone/something is like in the singular:
A hamster is an animal. Sarah is a very smart girl. Her dad is a mechanic.
Shakespeare is an English writer. Lisa has got a small nose.
3. We use a and an if the listener doesn't know which thing we mean:
Frank sat down on a sofa. (we don't know which sofa)
Do you have a bike? (it's not a particular bike)
4. We use a and an before phrases of time and measurements:
We can do these exercises in an hour. The mangos are $3.50 a kilo.
Our neighbours go on holidays three times a year.