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Using "An" and "A" (especially with Abbreviations and Acronyms)
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
- A house
- An hour


Using "An" and "A"
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." For example:
- Buy a house in an hour.
- An unknown goblin killed a unicorn.
- An LRS
- A TT race
- It would be a honour.
- Send an US ambassador.
- She was involved in a RTA.
(The abbreviation "RTA" starts with an "a" sound (i.e., "ar-tee-ay.")
Beware of Abbreviations
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.
- A LF transmitter was found in the basement.
Beware the Letter U
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.
Treat Acronyms Like Words Not Abbreviations
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." For example:- Tim worked in the air industry as a FOD inspector for a year.
- Jack was a FEDEX courier.
An Historical or A Historical?
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 better 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."
Interactive Test
Click on an or a:- Do you disagree with something on this page?
- Did you spot a typo?