When to Use An and A (Grammar Lesson)

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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.)

Click on an or a:



Abbreviations that start with the consonants F, H, L, M, N, R, S, and X attract an because they start with vowel sounds. For example:
  • An FRS representative will be present after lunch.
  • (FRS = Fellow of the Royal Society)
  • A LF transmitter was found in the basement.
  • (LF = Low Frequency)

Abbreviations that start with the vowel U attract a because U starts with the consonant sound y. For example:
  • A US ship spotted a U-boat.
  • An UFO landed in 1967.

An acronym is an abbreviation that is spoken like a word, e.g., BUPA, FOD, FEDEX. Therefore, as the first sound of FEDEX is f, use a and not an.

More examples:
  • Tim worked in the air industry as a FOD inspector for a year.
  • (FOD = Foreign Object Damage)
  • Jack was a FEDEX courier.
Read more about acronyms.

Letters and sounds do not always correlate in English.

When pronouncing the words historic and historical, the accent falls on the second syllable, and many pronounce them as starting with a vowel. For those people, it is appropriate to use an before historic and historical. Therefore, you have a choice depending on what sounds best for you.

There is a lot of leniency on this issue. If you're still unsure, opt for a historical and a historic as these remain preferable – especially in formal writing.

Read about the difference between historic and historical.

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