You learned in the early grades to use the article “a” before a consonant sound: a ball, a dog. You learned to use “an” before a vowel sound: an apple, an orange.
That rule applies when you are using an abbreviation or an acronym. Choose the article by the sound.
An abbreviation or acronym that is pronounced with a vowel sound takes “an”: an FBI agent (the abbreviation starts with an “eff” sound), an NCCU student (starts with an “in” sound), an AIDS researcher.
If an abbreviation or acronym is pronounced with a consonant sound, use “a”: a NATO official (it’s pronounced as a word beginning with a “nuh” sound), a UPS truck (begins with a “you” sound), a Ph.D. candidate.
This article was originally posted by the Raleigh News & Observer, a subsidiary of The McClatchy Co.; is posted here to provide continuity; and is copyright © 2011 The News & Observer Publishing Company, which reserves the right to remove this post.