Indefinite articles

In English, the two indefinite articles are a and an. Like other articles, indefinite articles are invariable. You use one or the other, depending on the first letter of the word following the article, for pronunciation reasons. Use a when the next word starts with a consonant, or before words starting in u and eu when they sound like you. Use an when the next word starts with a vowel (a,e,i,o,u) or with a mute h.

  • a boy
  • an apple
  • a car
  • a helicopter
  • an elephant
  • a big elephant
  • an itchy sweater
  • an ugly duck
  • a european
  • a university
  • a unit
  • an hour
  • an honor

The indefinite article is used to refer to something for the first time or to refer to a particular member of a group or class. Some use cases and examples are given below.

Use a to refer to something for the first time.

  • Would you like a drink?
  • I've finally got a good job.
  • An elephant and a mouse fell in love.

Use a with names of jobs.

  • John is a doctor.
  • Mary is training to be an engineer.
  • He wants to be a dancer.

Use a with nationalities and religions in the singular.

  • John is an Englishman.
  • Kate is a Catholic.

Use a with the names of days of the week when not referring to any particular day.

  • I was born on a Thursday.
  • Could I come over on a Saturday sometime?

Use a to refer to an example of something.

  • The mouse had a tiny nose .
  • The elephant had a long trunk .
  • It was a very strange car .

Use a with singular nouns after the words 'what' and 'such'.

  • What a shame !
  • She's such a beautiful girl .
  • What a lovely day !

Use a meaning 'one', referring to a single object or person, or a single unit of measure. In these sentences using "one" instead of the indefinite article is grammatically correct. It will add emphasis to the number, and contrast with other numbers.

  • I'd like an orange and two lemons please.
  • I'd like one orange and two lemons please.
  • The burglar took a diamond necklace and some valuable paintings.
  • I can think of a hundred reasons not to come.
  • I need a kilogram of sugar.
  • I need one kilogram of sugar.
  • You can't run a mile in 5 minutes!
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