Indefinite article has two forms: a and an.
a – we use before a noun or noun phrase beginning with a consonant
He’s a teacher.
We have a small garden.
It’s a nice dog.
an – we use before a noun or noun phrase beginning with a vowel
Would you like an orange?
She’s an electrician.
An egg for me, please.
We use indefinite article a / an only when we say about something first time, and described object or person is a countable noun in the singular
He’s got a game
Can you give me an address?[/example]
We never use indefinite article a / an before countable noun in the plural and before uncountable nouns. In such situations, we can use e.g some
There’s some milk in the fridge.
When we say about something second time (e.g in the next sentence), we have to use a definite article the.
She’s got an umbrella.
The umbrella is red.
We use indefinite article a / an only when we say about professions and nationalities in the singular [tooltip/link].
Tomas Carlsen is a Frenchmen.
My brother is a doctor.
He’s a driver.
If professions and nationalities are in plural we don’t use indefinite article a / an.
Tom and Mark are Englishmen.
My sisters are dancers.
If a noun is defined by an adjective (or few), we put an article at the front of it (or them)
He’s a handsome boy.
It was a long, tiring journey.
We use indefinite article a / an in phrases like a lot of, a few, a couple, a little.
I’ve got a lot of video games.
I have a couple of biscuits to share.
There are a few people in the cinema.