When to Use An and A (Grammar Lesson)

The Quick Answer
Use an before a word that starts with a vowel sound. If it does not start with a vowel sound, use a. For example:
  • A man
  • An elephant
But, look at this:
  • A house
  • An hour
The key word here is sound. It is not a question of whether the word starts with a vowel. It is a question of whether it starts with a vowel sound.

Using A and An

There is sometimes confusion about whether to use an or a, particularly with abbreviations. (The words an and a are known as articles.)

The sound of a word's first letter determines which to use. If the word starts with a vowel sound, you should use an. If it starts with a consonant sound, you should use a.

  • Buy a house in an hour.
  • (Although house and hour start with the same three letters (hou), one attracts a and the other an.)
  • An unknown goblin killed a unicorn.
  • (Although unknown and unicorn start with the same two letters (un), one attracts an and the other a. Remember, it is about the sound of the first letter.)
  • An LRS...
  • (LRS = Linear Recursive Sequence)
  • A TT race...
  • (TT = Tourist Trophy)
  • It would be a honour.
  • (The word honour starts with an o sound.)
  • Send an US ambassador.
  • (The abbreviation US starts with a y sound.)
  • She was involved in a RTA.
  • (RTA = Road Traffic Accident)
    (The abbreviation RTA starts with an a sound (i.e., ar-tee-ay.)

See Also

What are vowels? What are consonants? What are articles? What are adjectives? What are abbreviations? What are acronyms?