Indefinite Article

A singular countable noun always has an article or another determiner with it.

The indefinite article a/an is used to talk about one particular person or thing when the listener does not know which one is meant, or when it does not matter which one.

• She married an old man.
• They have a big house in the city.
• You had better consult a doctor.
• I saw a hawker selling his wares on the street.
• A man came and knocked at the door.

A/an is also used to talk about any one member of a class.

• A teacher must have patience. (=any teacher)
• A spider has eight legs. (=any spider)
• A dog is faithful to its master.
• A parrot can repeat what you say.

Cases where the indefinite article should not be used

With plural and uncountable nouns

The indefinite article cannot used before plural and uncountable nouns.

• Apples are red.
• Computers are expensive.
• Time is money.

With possessives

We cannot use the indefinite article with possessives. We use double possessives instead.

• He is a friend of mine. (NOT He is a my friend.)

With adjectives without nouns

We cannot use the indefinite article with an adjective alone (without a noun).

• She is a beautiful girl.
• She is beautiful. (NOT She is a beautiful.)