Indefinite articles in English (a and an) – (lesson with examples)

Indefinite articles in English (a and an)




Feel free to leave a comment if you find any errors or if you have any suggestions to make to improve this lesson.

The article a/an

We use A or AN when the thing or person we are talking about is not specific (it is “indefinite”):

  • I met a friend in New York.
  • I work in a school.

A/AN exists only in the singular, and only before a name that can be counted.

  • There is a book on the chair  (singular)
  • There are books on the chair  (plural)
  • There are a books on the chair ❌
  • There is water on the floor  (we can’t count water… so we put nothing here!)

We use a/an to talk about someone’s job:

  • He is a doctor  (we don’t say ‘he is doctor’)

We put A before a consonant (b, c, d, f, g, p, m, etc…):

  • a bear
  • a teacher
  • a table
  • a dog
  • a pilot

We put AN in front of a vowel (a, e, i, o, u):

  • an apple
  • an invitation
  • an elephant
  • an actor
  • an umbrella

Actually, it’s not that simple….

It’s the sound of the first letter of a word that determines whether we use a or an: if the word begins with a vowel sound, we use AN. If the word begins with a consonant sound, A is used.

Indeed, they say:

  • a university
  • a unicorn
  • a euro
  • a european
  • a user

⚠️ Even if hour, honor and x-ray start with consonants, we use “an” because they pronounce themselves as if they started with a vowel:

  • an hour
  • an honor
  • an x-ray

This is also why we use an when we talk about the letter F:

  • Your name is Francis, with an F? (NOT ‘with a F?‘)
  • He is an FBI agent (NOT ‘he is a FBI agent’)

Which is correct: “a one” or “an one”?

One is pronounced “wun,” so it sounds like a consonant, although it starts with a vowel : a one is correct.

  • I can’t see, is it a one or a seven? 


It’s not really a question of whether the word begins with a vowel or not, but with a vowel sound.

  • Buy a house in an hour = house and hour start with the same letters but pronounce differently!
  • An unknown woman saw a unicorn = same thing, unknown and unicorn start with the same letters but pronounce themselves differently. Either A or AN is used depending on the sound!

Remember that it’s the sound that is important!

⚠️ Herb & Hospital: it depends!

Do we say a hospital or an hospital?  The letter H of these two words is pronounced or not depending on whether you have an American or British accent. In American english, the H is silent, so it looks more like an herb, a hospital…

Defined (the) or indefinite (a, an) article?

Finally, look at the following example to understand the difference:

  • Pass me a cup  (any one)
  • Pass me the cup  (a precise cup)
  • I need a pen  (any one)
  • I need the pen  (a specific pen)


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