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I wonder what is the correct usage, my assumption is that it is based on how you pronounce it, like for example:

an SQL query => pronounced an ess cue ell query ,

an XP OS => pronounced an ex pee oh ess ,

an HTML script => an aitch tee em ell script ,

a USB port => a you ess bee port ,

a USA citizen => a you ess aih citizen .

Is that correct or not, and why?

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Not only is this the #2 most frequently asked question on ELU, it shares much in common with the #1 question, too. –  tchrist Feb 27 '13 at 15:14
We also have a comprehensive blog post. –  RegDwigнt Feb 27 '13 at 15:30
Note that H is pronounced aitch and haitch, depending on the area of the country. Therefore HTML script can become "An aitch tee emm ell script" or "A haitch tee emm ell script" in spoken English. –  Jon Story Feb 27 '13 at 15:36
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marked as duplicate by tchrist, KitFox Feb 27 '13 at 15:15

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2 Answers

up vote 1 down vote accepted

You have it exactly right: use a before a consonant sound and an before a vowel sound. If the abbreviation is read as its letters, the initial sound of the name of the first letter dictates.

I would make two notes, however. First, either article may be acceptable in cases where there are multiple accepted pronunciations, one starting with a vowel sound and one with a consonant sound. For example, an history is generally a hypercorrection for a history in American English, since Americans almost always pronounce the h. But it isn't strictly incorrect, because there are dialects of English where the h is dropped. Some abbreviations (initialisms as another answer points out) are read as letters, others (acronyms) as words, and depending on the author's usage you may see both

  • an SQL query = an ess cue ell query
  • an FAQ document = an eff aiee cue document
  • an NAS system = an enn aiee ess system


  • a SQL query = a sequel query
  • a FAQ document = a fack document
  • a NAS system = a nazz system

The key in your writing (and speaking) is to be consistent. There are many opinions in the technology world about how to vocalize a term; try a web search on "gif pronunciation" some time.

Second, as a matter of usage one can be a U.S. citizen, a United States citizen, an American citizen, or a citizen of the United States of America, but one is hardly ever referred to as a USA citizen.

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That's correct. We associate the indefinite article with the vocalization of the first letter in initialisms (acronyms that are pronounced as letters and not words. See: NASA [acronym] vs. FBI [initialism]). Thus, "an SQL query" because, while "S" is a consonant and words beginning in consonants take an "a", the first vocalization of the letter "s" is a vowel.

S = ess.


"An SQL query"


B = bee


"A BA in Chemistry"

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