Using a and an

A or an are used before countable nouns to talk about something the listener or reader does not know about.

  • I was born in a town.
    (The reader doesn’t know which town and no vowel sound so a.)
  • They are a company which sells chocolate.
    (Lots of companies sell chocolate so, the listener doesn’t know which company is being talked about and no vowel sound so a.)
  • I want to buy an umbrella.
    (There are lots of umbrellas to buy, but we don’t know which one. Here there is a vowel sound, so we use an.)