Should I use "a" or "an" when I abbreviate a word?



Taking notes, I was going to write this:

therefore p′ is a shortest path.

But the topic is APSP which stands for "all pairs shortest paths" so I decided to just write SP instead and...

Is it written with a like this

therefore p′ is a SP

or with an like this (because in my head I would "read" the S)

therefore p′ is an SP


Posted 2018-01-08T15:42:15.780

Reputation: 471

Maybe this is a jargon thing, but shortest means the one with the least length. There can only be one such shortest path in most cases, unless another is identical, in which case you'd normally say "one of the two shortest paths". – Jim MacKenzie – 2018-01-09T14:50:58.760

4@JimMacKenzie: When you want to fly from the north pole to the south pole, there are infinitely many different shortest paths that you could take. Situations like these are quite common occurrences, especially in science and technology, and so talking about a multitude of shortest paths (or largest objects, most cromulent words, ...) is a perfectly normal thing to do in these contexts. – RQM – 2018-01-10T11:48:01.047

You might also consider that whether you use “a” or “an” would encourage people to pronounce “shortest path” or “ess pee” respectively. – gen-ℤ ready to perish – 2018-01-10T12:55:59.647



Whether you say a or an is determined by the pronunciation of the next word, and nothing else. If the next word begins with a consonant sound (not necessarily a consonant letter!), you say a, and if it begins with a vowel sound (not necessarily a vowel letter!), you say an.

So yes, you are correct: if you write or read "SP", you would say "an SP", because "ess" begins with a vowel sound.


Posted 2018-01-08T15:42:15.780

Reputation: 25 636

17I don't think the answer is this simple, although I admit I don't have the answer. When you read some abbreviations, you pronounce them as initialisms in your head. Others, you don't. For example, Some people will read "45 mpg" out loud as "forty five miles per gallon," and others as "forty-five em-pee-gee." Some will read "59 m" as "59 meters." I don't know of anyone that would read it out loud as "59 em." The same can be said of reading "SP." Some people will read it out loud as "ess pee" and others might read it out loud as "Shortest path." Incidentally, I'm in the latter category. – Syntax Junkie – 2018-01-08T17:42:46.980

9@RandallStewart Well, yeah: the pronunciation of the next word, whether you pronounce it as "ess pee" or "shortest path", but if you write "an SP doodad", that's a pretty big clue you intended it to be read as "an ess pee doodad". I'm trying to think of an example in which you would put an article directly before a something you don't spell out, but I'm not coming up with one. – stangdon – 2018-01-08T17:52:58.473

3But that's only an issue if you write "a/an SP". If you write "a shortest path", then there's no question that "shortest path" is pronounced "shortest path". To say that someone might read it "SP in his head ... by that reasoning, if I write "a state in the west" I should use "an" because someone reading that might think of Idaho. :-) – Jay – 2018-01-08T17:58:49.827


An example for your comment would be "an FBI agent" as I don't think someone would read that as "a Federal Bureau of Investigation agent". I think people tend to read abbreviations as letters if the abbreviated text is long, but there is a thick line between what's short and what's long (an example would be "shortest path", we can't tell for sure if it's going to be read "ess pee" or "shortest path").

– ibrahim mahrir – 2018-01-08T22:12:24.720

1... also if the abbreviation is universally known to be read as letters. – ibrahim mahrir – 2018-01-08T22:16:18.187

@stangdon "if you write 'an SP doodad', that's a pretty big clue" In practice, people commonly write it as if they're pronouncing the non-abbreviated form. While I don't do that myself, I see there's fair motivation behind it: read in full, write abbreviated. – jpaugh – 2018-01-08T22:46:39.603

2@jpaugh - Well, it depends. Some abbreviations are commonly written as if they were spelled out (FBI, CIA, USSR), and some aren't (SCUBA, RADAR). There isn't a hard and fast rule on that, AFAICT. – stangdon – 2018-01-08T23:16:20.443

@Jay I don't really understand your comment, I'm afraid. I interpreted the OP's question as just being "If I write SP doodad, should I use a or *an?" That's it. Nothing about whether they might read it as SP in their head if you wrote "shortest path". – stangdon – 2018-01-08T23:18:20.723

2The most common ambiguous example is probably FAQ. Some people pronounce it eff-ay-queue, in which case it would be "an FAQ" but others pronounce it fack in which case it would be "a FAQ". – TripeHound – 2018-01-09T02:52:12.927

1@stangon Not necessarily. If you saw, "MB of data," wouldn't you read that aloud as "Megabyte of data"? Have you ever heard someone refer to "An em-bee of data"? If a director sends you a note to "Make a S.L. exit," don't you read that aloud as "Make a stage left exit?" If kit tells you to "Connect the RED wire to pin 6, the BLU wire to pin 8, and the GRN wire to ground," don't you still read that aloud as the actual color names? See other examples in an answer I left. I just adopted a "DST cat," but the shelter worker still spoke it as "Domestic Short Hair." – Syntax Junkie – 2018-01-09T13:02:49.210

7Also note that the writer's choice to use a/an often expresses an intent to the reader for how the abbreviation/acronym should be read. – R.. GitHub STOP HELPING ICE – 2018-01-09T18:51:46.430

2@RandallStewart: Many units abbreviations are appropriate only following numerals. One might measure a signal of 3V, but three volts. I might speak of a "kay-byte" using a definite or indefinite article, but I don't think I'd write that (note that "kay" is the pronunciation of the uppercase "K" meaning 1024, while "kilo" is the pronunciation of the lowercase "k" meaning 1000). – supercat – 2018-01-09T20:42:27.940

@supercat That's a good point. Thank you for the correction. – Syntax Junkie – 2018-01-09T21:46:43.223

You're describing the difference between "initialisms" (pronounce the letters; e.g. HTTP) and "acronyms" (pronounce as though it were a word; e.g. radar). – fectin – 2018-01-09T22:56:28.557

So here’s a challenge: an ROTC scholarship or a ROTC scholarship? Some people say “are-oh-tee-see” and others say “rot-see”. – Todd Wilcox – 2018-01-10T02:28:55.950

@RandallStewart i would say "em-bee", "ess-ell", "red, green, blue", and "dee-ess-tee" respectively. The red green blue one is a bit different though, because they aren't abbreviated, just shortened. Also, i'm one of the terrible people that say "ell-oh-ell" instead of "laugh out loud". These are what i most commonly hear from others. I don't know if i've heard anyone say the whole word "megabyte" since my sixth grade science teacher. – None – 2018-01-10T05:16:02.273

1@ToddWilcox: write it the way you'd say it (or to be precise, write it the way the voice you're writing in would say it). If the reader says it differently, that's their lookout, but generally speaking we don't refuse to listen to people just because they speak differently from how we speak. A grammar pedant is someone who chooses to do that: anecdotally they seem especially prone to doing it in written media ;-) – Steve Jessop – 2018-01-10T10:10:04.550

@AytAyt You have enlightened me. I probably do fall into the age group of your sixth grade science teacher. That does highlight the OPs question: When different people are likely to pronounce an abbreviation different ways, and the different pronunciations would require different article adjectives, is there a rule to guide a writer which one to use? The answer is no. There is no rule. The writer is free to choose. (But you really say em-bee instead of megabyte? Wow. We really do travel in different circles!) – Syntax Junkie – 2018-01-10T13:33:09.787


These are actually called acronyms or initialisms. The few editing guides I checked (like this one from the American Psychological Association) say to use this guide:

The general rule for indefinite articles [before acronyms] is to use a before consonants and an before vowels. The trick here is to use your ears (how the acronym is pronounced), not your eyes (how it's spelled).

This means you have to "sound out" the word in your head to tell if it starts with a consonant sound or a vowel sound. Examples:

I checked this answer with an APA editor. (ayy pee ayy)

Today an FBI agent came to our office. (eff bee eye)

Today a CNN reporter asked me questions (cee enn enn)

Today an NBC reporter asked me questions (enn bee cee)

However, this depends on whether you commonly sound out the individual letters, or if the acronym is usually pronounced as a word. For example, a LAN (computer network) is usually pronounced as it's spelled, so you would say:

a LAN schematic

Similarly SAM, SIM, SCUBA, GIF, JPEG, ZIP, LASER, IMAX, and others.

Other examples:

  • a FASB rule; an FOB airfield
  • a LAN schematic; an LAPD memo
  • a MOMA exhibit; an MRI test
  • a NICU nurse; an NPO order
  • a SAM base; an SAT exam

(Edit) To add further complication: As choster mentions below, not everyone pronounces all of these kind of abbreviations the same way. For example, with SQL, some people say "ess cue ell" and others say "sequel".

In the first case you would say, "an SQL query" and the second, "a SQL query"


Posted 2018-01-08T15:42:15.780

Reputation: 85 521


APA, FBI, CNN, NBC are not acronyms, which are pronounced as words. They are merely garden-variety abbreviations, or, if you prefer, initialisms. (See the Can be confused and Grammar note sections at any of those links.) OTOH, I have heard NICU pronounced "NICK-you" (ˈnɪk-ju), and I think I have heard MOMA pronounced ˈmoʊ-mə.

– shoover – 2018-01-08T18:24:15.163

3@shoover good to know, but your own link contradicts you with the second definition. Initialisms, while accurate, isn't common parlance. – Andrew – 2018-01-08T18:47:20.853

which is why I said "See the Can be confused and Grammar note sections at any of those links." I think this is degenerating into a prescriptive vs. descriptive argument. – shoover – 2018-01-08T19:45:46.027

2I can confirm that "nick-you" is what all the doctors and nurses say at least in the US. – mattdm – 2018-01-08T22:04:54.657

3A FOB (forward operating base) is, at least in the US military, pronounced fob, not via initials. – TemporalWolf – 2018-01-08T22:44:26.983

1A database program I once developed for offered both an SQL and a SEQUEL interface. They were similar but distinct query languages. (As I recall SEQUEL was a follow-on to QUEL.) The database vendor's trainers and support folks were very sensitive about carefully distinguishing between them. – Adrian McCarthy – 2018-01-09T19:22:37.900

@shoover What? APA, FBI, CNN and NBC are acronyms.

a set of initials representing a name, organization, or the like, with each letter pronounced separately.

LOL. The can be confused part, literally lists acronym as well. – NiCk Newman – 2018-01-09T19:40:18.340

1@NiCkNewman As shoover said, we're getting into descriptive vs prescriptive, but most people I know use acronym to refer to an initialism that is pronounces as a word, like radar or OPEC, not for other abbreviations where each individual letter is pronounced, like ACA or AMA. – Kevin – 2018-01-10T19:49:04.100

Well, yeah, but it still logically falls under the 2nd definition. To claim they are not acronyms is simply untrue. – NiCk Newman – 2018-01-10T19:53:46.093

@AdrianMcCarthy: praise them for that. After few "historical" articles have shown up over the last years, more and more people try to stand out using "historically correct pronounciation" of .. sequel. We've got T-SQL from Microsoft, PL/SQL from Oracle, whatever, that's all xxSQL, so they read it sequel (although! NoSql is always read no-ess-cue-ell, go figure).. I understand that saying 'sql' instead of full name is handy, but I still hate the sound of sequel. No body says tee-sequel nor pee-ell-sequel. – quetzalcoatl – 2018-01-10T21:43:44.270


I've left a comment already, and the OP has already selected the accepted answer, but I feel compelled to leave a full answer of my own because it feels like there are a number of loose ends.

First, it's well established that the use of a vs. an is determined by the sound that comes next, not necessarily the written letter. The Chicago Manual of Style (16th edition) puts it like this:

"A comes before words with a consonant matter how the word is spelled {a eulogy}"

But the OP seems to understand this already, based on the wording of his text. The title of this question has to do specifically with abbreviations. Here things get tricky. You should still chose the article adjective based on the sound it precedes. But when an abbreviation can be pronounced more than one way, and the pronunciation determines the article, how do you pick the correct article?

Some abbreviations are almost always pronounced as the full word or phrase that they represent:

  • "A Mrs. Smith called you right after you left." (Not: "An Emm-Are-Ess called you...")
  • "Please bring a no. 2 pencil." (Not: "Please bring an En-Oh two pencil.")
  • "We traveled in a NW direction." (Not: "We traveled in an En-Double-Yoo direction.")
  • "A He-filled balloon (Not: "An aitch-ee filled balloon.")

Some abbreviations (intitialisms) tend to be pronounced letter by letter, while others (acronyms) tend to be prounounced as single words:

  • An FBI investigation, An AT&T investment.
  • A Radar detector, a Scuba instructor

That leaves the 3rd class of abbreviations: Their pronunciation hasn't settled into a standard form yet. I think this is the part of the OP's question that the other responses haven't addressed and that feels like a loose end.

  • NICU: This is sometimes pronounced En-Eye-See-Yoo or Nick-Yoo. (Example from Shoover above.)
  • SQL: Pronounced as an initialism or an acronym (Example from Andrew above).
  • ROTC (Reserve Officer Training Corp): Pronounced as "rot-see" or "are-owe-tea-sea" (example from Todd Wilcox above)
  • FAQ (Frequently Asked Questions): Pronounced as "fack" or "eff-ay-cue" (example from TripeHoward above)

So in print: For abbreviations without a traditional, well-understood pronunciation, how do you choose the correct article adjective? How do you know if an abbreviation is meant to be read out loud as:

  • the full word?
  • an initialism?
  • an acronym?

The use of all caps is no help. For example, if read out loud, don't you pronounce TBSP as "Tablespoon" and BLVD as "Boulevard"? I've seen Stack Exchanged abbreviated as "S.E.," but don't you still read that aloud as Stack Exchange?

I would put the OP's "SP" in this category since it's a non-standard abbreviation that the OP came up with him/herself. I can think of three options to pick the right article:

  • Mention early in the paper how the authors pronounce the abbreviation, and then use the appropriate article adjective. (This feels stodgy, but it could be helpful for an uncommon abbreviation that, nonetheless, still has a standard pronunciation in a certain field or context.)
  • Reword the sentence to avoid the ambiguity. (This is a good old fallback, but it sort of avoids the question rather than answer it.)
  • The Chicago Manual of Style has this to say:

"Before an abbreviation, a numeral, or a symbol, the use of a or an depends on (or conversely determines) how the term is pronounced." [emphasis mine]

In other words, you can choose whichever article adjective you prefer, and that should guide the reader how you intend the abbreviation to be pronounced.

Syntax Junkie

Posted 2018-01-08T15:42:15.780

Reputation: 389

2TBSP: Nope; didn't realize it was an all-caps version of Tbsp. BLVD - can't tell (I scanned Boulevard at the same time as BLVD, but probably "no"). I might give a different answer if there was a bit more context to prompt me (a discussion of recipes or street addresses). On the other hand I definitely read "S.E." as "ess ee", not "stack exchange". Note that Tbsp and Blvd are different to SE and SP. The former pair are abbreviations of a single word, and the latter pair are abbreviations of phrases from their initial letters (which is why I find TBSP and BLVD wrong). – Martin Bonner supports Monica – 2018-01-10T08:14:05.333


The general rule is that when the initial letter of a word has a consonant sound, article "a" takes precedence and when it's a vowel sound, article "an" is used. This however depends on the pronunciation of certain words inform of initials, acronyms or abbreviations.


Posted 2018-01-08T15:42:15.780

Reputation: 9

Yes, but the question is tangled between the abbreviation and the vowels and the non definite article. – Kentaro – 2018-01-10T17:38:59.753