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99% of the time, I'm clear on when I should use "a" versus "an." There's one case, though, where people & references I respect disagree.

Which of the following would you precede with "a" or "an," and why?

  • FAQ

[Note: I've read the questions "A historic..." or "An historic…"? and Use of "a" versus "an", but the rules given there don't necessarily apply here.]

[Edited to add]

Here's a shorter (and hopefully clearer) version of the question… In written English, which is correct (and why): "a FAQ" or "an FAQ"?

Some references with differing opinions:

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"An RPG". The controlling factor is whether it's spoken with a vowel sound. (So "an hour", "a unicorn", etc.) – chaos Feb 6 '11 at 4:46
This does raise questions about when there are multiple common pronunciations of the acronym. Like "SQL" is sometimes pronounced "es-kew-el", and sometimes "sequel". The former would call for "an" and the latter for "a". I think, though, that we always choose "a" or "an" based on pronunciation of the acronym and not the spelled-out words, e.g. "an SST", as in "an ess-ess-tee", not "a supersonic transport". – Jay Sep 30 '11 at 14:32
@Jay SQL: In which case the writer picks their own style (or follows the in-house style) and uses it consistently. – Hugo Sep 30 '11 at 15:10
Or rephrases all sentences with SQL to avoid putting either "a" or "an" in front of it. – yoozer8 Sep 30 '11 at 17:25
@Jim: While I admit to sometimes rephrasing a sentence to avoid a spelling or grammar problem, that is the coward's way out! – Jay Oct 4 '11 at 15:09
up vote 157 down vote accepted

It depends on whether the abbreviation is an acronym or an initialism. As "fubar" and "scuba" are usually pronounced as a word (making them acronyms), it would make sense to say "a fubar" and "a scuba diver". "FAQ" is a bit harder, because I have heard people say it like an initialism: "‹f›‹a›‹q›", while others pronounce it as an acronym /fæk/. Therefore, one should write either "a FAQ" or "an FAQ" depending on how that person pronounces it, ie, whether it is an acronym or an initialism.

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+1 Exactly, it depends on how you pronounce these acronyms. – b.roth Aug 16 '10 at 8:21
Thanks for the teaching :-) Indeed there is a difference in the strict sense :-) So is CD-ROM an acronym or an initialism? – Vincent McNabb Aug 16 '10 at 9:08
@Dori - yes. Whichever way you write it, it will trip up some readers. The Corpus of Contemporary American English (COCA) lists two results for "a FAQ", and one result for "an FAQ", so "a FAQ" is probably more common. Google also shows a preference for "a FAQ". – Vincent McNabb Aug 17 '10 at 0:12
The whole “ acronyms must be pronounced as words” distinction appears to be one that is only made by dictionaries. From what I can tell, any abbreviation that is made from initials is called an acronym if it is pronounced differently from what the initials stand for. – nohat Aug 18 '10 at 14:56
It appears that the answer is: "there is no definitive answer to this question." Not exactly what I'd hoped, but as this was the only answer that responded to the question I asked, I guess that makes it the best. – Dori Aug 20 '10 at 4:04

The important point to remember is the following:

Written language is a representation of the spoken word.

Thus, the answer is "If the word following the indefinite article begins with a vowel sound, use an; if it begins with a consonant sound, use a."

In the case of initialisms and acronymns, use the exact rule above. For initialisms (e.g. "US"), the individual letters are pronounced. With what sound does the first pronounced letter begin? In the example "US", the first sound is /j/ (or "y"). This is a consonant sound, despite the letter "U" being a vowel; thus, you use a, as in a US dollar.

Contrast this with the initialism "RPM", which begins with the consonant "R" but is pronounced starting with /a/; thus, you use an, as in an RPM counter.

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I'd ++ this if I could... Provides an excellent tutorial on letter sounds as well. Very nifty! Thank you. – Shanimal Dec 20 '12 at 15:05

Note: Some of this information may be extraneous, but take it for what you will!

In general, some acronyms represent nouns, others verbs or adjectives. If it represents the former, I see no problem with prefixing with an (in)definite article (a/an).

scuba is listed as a noun (lower-case) rather than an acronym in most dictionaries these days. It is of course derived from an acronym, but has evolved into a word in its own right (laser would be another example).

FAQ is an acronym, but is very commonly used as a noun - "a list of frequently-asked questions".

FUBAR has various definitions, but it's normally interpreted as an adjective (at least by the original military one).

Hence, I would happily prefix scuba/SCUBA with a/an, but definitely not FUBAR.

All these words begin with hard consonants, and thus should always be prefixed with a. Saying that, some people pronounce FAQ by spelling out its letters, in which case an is appropriate. I've never heard this done with the other two.

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When used in the military sense, "fubar" would not have a(n) before it. However, when used in other senses where it is a noun, it would be perfectly fine. It would also be fine to say, "Man, this is a fubar situation". As the article refers to the noun, "situation", which is being modified by the adjective, "fubar". – Vincent McNabb Aug 16 '10 at 9:26
@Vincent: Yeah, but that's slightly beside the point. I mentioned that fubar is used as an adjective, this 'a' is just applying to the 'situation'. – Noldorin Aug 16 '10 at 10:13
@Noldorin I agreed with your point and added extra information. You are welcome to edit your post and clarify. – Vincent McNabb Aug 16 '10 at 10:45
The question is which to use between "a" and "an", not whether to use them. The part of speech has nothing whatever to do with this question: it's all on the pronunciation. – Colin Fine Aug 16 '10 at 13:20
@Colin: The question was not clear to me. It seemed to be asking too different things. Just because I provided more info that may have been necessary, think twice whether that really deserves a down-vote. – Noldorin Aug 16 '10 at 13:33

The rule about the usage of a and an as indefinite articles is that an is used before a vocal sound.

  • A warranty (/ˈwɑːrənti/)
  • A user (/ˈjuːzər/)
  • A one-way (/ˈwən ˌweɪ/)
  • A man (/mæn/)
  • An angel (/ˈeɪnʤəl/)
  • An information (/ˌɪnfərˈmeɪʃən/)

When used before an acronym, the rule is still valid, but which article to use depends from how the acronym is pronounced (letter by letter, or as a word).

  • An MP3 (/ɛm pi θri/)
  • An RPG (/ɑːr pi ʤi/)
  • An FBI agent (/ɛf biː aɪ/)
  • A GPS device (/ʤi pi ɛs/)
  • A NASA employee (/ˈnæsə/)
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The definition of acronym I know is not related with the fact I pronounce it as word, and the NOAD reports initialism also as synonym of acronym. – kiamlaluno Feb 6 '11 at 5:20
@chaos: You wrote that mostly only professional technical writers draw the distinction; what is reported from a dictionary (like the NOAD, which is New Oxford American Dictionary) is not the point of view of only professional technical writers, but the meaning of a word/phrase given from most the speakers. – kiamlaluno Feb 6 '11 at 6:32
@chaos: linguists and etymologists don't speak only of the language used by linguists and etymologists. Then, do linguists cite articles on Wikipedia? ;-) – kiamlaluno Feb 6 '11 at 6:55
@chaos: The distinction between acronym and initialism is a neologism that is not maintained by all writers or dictionaries. In fact, the Wikipedia page you linked cites The Cambridge Encyclopedia of the English Language: "However, some linguists do not recognize a sharp distinction between acronyms and initialisms, but use the former term for both" and Merriam-Webster's Dictionary of English Usage: "A number of commentators […] believe that acronyms […] pronounceable as words. Dictionaries, however, do not make this distinction because writers in general do not." Etc. – ShreevatsaR Feb 6 '11 at 11:53
@chaos: As a linguist, I don't consider people's actual usage to be the "lowest common denominator". Why should a self-declared grammar authority's arbitrary decision about the meaning of a word be inherently more "correct" than the way people actually understand the word? Language often isn't precise. There are those who construct artificially precise categories for English lexical items (that don't reflect usage) and then view those who don't conform to those distinctions as being sloppy or poor in their command of English. I see that as a waste of time — we don't learn anything that way. – Kosmonaut Feb 8 '11 at 14:33

It doesn't make any difference at all whether the article is modifying an acronym, an initialism, a proper noun, a French borrowing, or anything else. English article form is determined solely and entirely by pronunciation. And not at all by spelling.

The rule for the pronunciation of articles in English -- definite and indefinite -- is that they have one form before consonants (note, real consonants -- sounds -- not "letters" in a writing system), and a different form before vowels (ditto).

Hence, how you say it is what counts. Nothing else does.

  • Before vowels -- Indefinite an /ən/ and Definite the /ði/:
    an hour, an SOS, an A-to-Z selection, an EE degree, an idiot
    the hour, the SOS, the A-to-Z selection, the EE degree, the idiot (all pronounced /ði/)

  • Before consonants -- Indefinite a /ə/ and Definite the /ðə/:
    a URL, a snafu, a Charlie Foxtrot, a moron
    the URL, the snafu, the Charlie Foxtrot, the moron (all pronounced /ðə/)

Most native English speakers never notice that there are two different pronunciations for the, but non-native English speakers need to know this immediately.

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+1 for pointing out the two pronunciations of the. – Bradd Szonye May 28 '13 at 23:20
+1 ditto Bradd's comment – TrevorD Jun 9 '13 at 18:54
I believe there are three pronunciations. – Edwin Ashworth Mar 26 '14 at 16:55

Vincent McNabb is correct. If you want evidence based on "credible and/or official sources" that this is the rule followed in formal English writing, here is my suggestion.

I ran Google searches on Google Books only, meaning the bulk of the search will be against professionally edited and published works, not random web sites. I searched only for phrases where the pronunciation of the acronym was relatively clear and consistent: for example, nobody pronounces "SCUBA" as "Ess Cee Yew Bee Ay" and nobody pronounces "FBI" as "Fibbi."

Here are the number of hits in the Google Books database for:

  • "A SCUBA": 49,800
  • "An SCUBA": 56

  • "A FBI": 16,000
  • "An FBI": 343,000

  • "A NASA": 264,000
  • "An NASA": 16,500

  • "A RGB": 7,130
  • "An RGB": 33,800

  • "A UPC": 11,800
  • "An UPC": 436

In each case, basing the article on the initial sound, rather than on the initial letter, is more common; in most cases substantially more common.

As a control, I also looked at two acronyms where both the initial sound and the initial letter are consonants.

  • "A VPN": 50,100
  • "An VPN": 960

  • "A OCR": 9,380
  • "An OCR": 1,870,000

Because "An VPN" and "A OCR" are incorrect based on any possible rule, we can conclude that the positive results are grammatical, OCR, or search engine errors. This suggests that the minority viewpoint on SCUBA, FBI, NASA, RGB and UPC are also smaller than they appear.

We can conclude that, based on evidence of usage among published documents digitized by Google Books, the preferred rule is to base the article on how the intended pronunciation of the acronym would be spelled phonetically.

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Like @Vincent McNabb said, it is a question of whether the word is used as an initialism (like HTML) or a acronym. When in doubt, as with FAQ, I would defer to the initialism form ("a FAQ") as it suggests in Wikipedia:

There is also some disagreement as to what to call abbreviations that some speakers pronounce as letters and others pronounce as a word. For example, the terms URL and IRA can be pronounced as individual letters: /ˌjuːˌɑrˈɛl/ and /ˌaɪˌɑrˈeɪ/, respectively; or as a single word: /ˈɜrl/ and /ˈaɪərə/, respectively. Such constructions, however—regardless of how they are pronounced—if formed from initials, may be identified as initialisms without controversy.

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protected by RegDwigнt Feb 4 '12 at 18:17

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