There is sometimes confusion about whether to use 'an' or 'a' (particularly with abbreviations). 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'.
Using A and An
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.
(LRS - Linear Recursive Sequence)
A TT race...
(TT - Tourist Trophy)
It would be a
('honour' - starts with an o sound)
Send an US ambassador.
('US' - starts with a y sound)
She was involved in a
('RTA' - Road Traffic Accident)
WATCH OUT FOR THESE |
Abbreviations that start with the consonants F, H, L, M, N, R, S and X attract an, because they start with vowel sounds.
An FRS representative will be
(FRS - Fellow of the Royal Society)
A LF transmitter was found in the basement.
(LF - Low Frequency)
WATCH OUT FOR U
Abbreviations that start with the vowel U attract a, because U starts with the consonant sound
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.
Tim worked in the air industry as a FOD inspector for a year.
(FOD - Foreign Object Damage)
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 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.