A Vs. An

So I genuinely became interested in this little debate on my Formspring so I decided to do a little research.

This is what I found:

Use the following rules when using ‘A’ or ‘An’.

  1. Use “A” before all words that begin with consonants.
    • a pet
    • a door
    • a green onion
    • a cat
  2. With one exception: Use an before unsounded h.
    • an honorable peace
    • an honest error
  3. Use “An” before all words that begin with vowels:
    • an apple
    • an elbow
    • an Indian
  4. With two exceptions: When u makes the same sound as the y in you, or o makes the same sound as w in won, then a is used.
    • a union
    • a united front
    • a unicorn
    • a used napkin
    • a U.S. ship
    • a one-legged man

It surprised me as well, but apparently that’s how it’s done. I have also checked multiple websites which also state the same.

Don’t believe me, google is your friend.

Source: Purdue OWL