A vs an: choosing the indefinite article

A typical slip

He described it as an utopia.

He described it as a utopia.

The rule

A or an depends on the sound, not the letter

A and an introduce one countable thing that is new to the listener. The choice between them follows the first sound of the next word.

a
Before a consonant sound, including the “you” and “w” sounds. a book · a university · a utopia · a one-way ticket
an
Before a vowel sound, including a silent h. an apple · an hour · an honest man · an MBA
One of many
A first mention, a job, one of a kind. I saw a film yesterday. · She is a doctor.

Part of the guide

What YabLab does with this mistake

  1. Catches it right as you write — comments, email, docs.
  2. Explains the why in your language, not just the fix.
  3. Helps you practice it until it is gone for good.

Related mistakes