Plurals of acronyms, abbreviations, initialisms and single letters

Plurals of acronyms, abbreviations, initialisms and single letters do not usually take apostrophes. Guidance on this issue is not unanimous, but some general advice can be consistently applied, and may help resolve some of the widespread confusion that seems to be generating even more widespread confusion.

Stan Carey - Twitter Trending TopicsPictured is a screenshot from Twitter, taken a few months ago, showing popular subjects or “Trending Topics”. The vast numbers of people using Twitter means that for a subject to become a “Trending Topic”, it needs to be mentioned a great deal. Because the software distinguishes between two words that are identical apart from the presence or absence of an apostrophe, both “SATs” and “SAT’s” have the potential to appear concurrently in the list, as indeed they did. Evidently, both forms are widely used. My preference is for “SATs”, and I would consider “SAT’s” ill-advised, because such apostrophes are largely unnecessary and potentially confusing.

A recent report from TechCrunch illustrates the potential for miscues from apostrophised plurals:

Stan Carey - TechCrunch on

Readers could easily begin reading the sentence “The URL’s already shortened…” and think that “URL’s” is a contraction of “URL is (or has)”: “The URL is (or has) already shortened…” These miscues would cause only minor irritation, but why invite them at all? The problem is easily and sensibly avoided by adopting the widespread convention of adding ‘s’ to form a plural. This is what Nambu Networks, the company TechCrunch are reporting on, have done (see the bottom line in the screenshot). Unnecessarily apostrophised plurals, as well as being unsightly, almost certainly increase general confusion about plural formation. Examples are endless.

Grammar is a minority interest, so it is unsurprising that this usage has become common. So many people have seen signs like the abovelinked, or ads for “CD’s” and “DVD’s”, that they reasonably assume this to be the standard or “correct” form. As a convention it is well on the wane. Most modern advice recommends including an apostrophe only if there is a danger of misunderstanding or ambiguity. So we have ABCs, ATMs, CDs, CD-ROMs, CEOs, CPUs, DTs, DVDs, EEGs, GDPs, GCSEs, GPs, IOUs, IQs, MAs, MPs, NGOs, PCs, PhDs, SATs, SMEs, SOSs, TVs, UFOs, URLs, VCRs, VIPs, WMDs, and so on. Inserting apostrophes in some, e.g. ABC’s, is not an offence to legibility, but I would consider it dubious and unnecessary. That goes for initialisms ending in ‘S’, too.

“Sellers of CDSs [credit-default swaps] had no such record to consult.” (The Economist, 8 Nov. 2008)
“Modern EEGs work on the same principle as the sprung mirror galvanometer” (Empson, Sleep and Dreaming)
“Treasury bills (TBs) are short-term UK government IOUs of three months’ duration” (Blake, Financial Market Analysis)
“Finally, we must consider what class of NLPs can be treated by PWL approximation using SOSs” (Hartley, Linear and Nonlinear Programming)

Incidentally, I searched the British National Corpus for examples of “WMDs”, but I didn’t find any:

Stan Carey - search for WMDs

Much as I love the Corpus, I never expected it to deliver such a hearty Monday laugh.

Some abbreviations are also commonly or occasionally written with full stops, for example academic qualifications and country names. When these are pluralised, -s or -‘s can be added: D.T.s or D.T.’s, G.I.s or G.I.’s, Ph.D.s or Ph.D.’s. There’s a fair argument that an apostrophe here increases clarity. Some abbreviations already stand for plurals, e.g. U.S. (or US) for United States. So there is no need for USs, U.S.s or U.S.’s, except the latter as a possessive. Abbreviations of length, volume, weight and time are usually left unchanged, i.e. without appending either -s or -‘s, e.g. ft., min., sec., lb., oz. There are a few common exceptions: yrs., hrs. Many such abbreviations are often written without the full stop: mm, cm, km, oz, lb. This is fine.

The apostrophised form is also accepted with pluralised single letters. In fact, it is sometimes recommended to avoid confusion: Mind your p’s and q’s, dot your i’s and cross your t’s. This is not grammatical, but it is typographically justifiable. Italics are also okay: Mind your ps and qs, dot your is and cross your ts – but this presentation can be too subtle for some eyes, fonts, and publishing houses. Upper case letters are clearer: Mind your Ps and Qs. But this increase in clarity can be negligible: Dot your Is. So the preferred option for this last example would be to include an apostrophe, especially with lower case i’s, or to wrap the letter in quotation marks: Dot your “i”s and cross your “t”s. In essence: with single letter plurals, if there is the possibility of ambiguity or confusion, apostrophes are preferred but not necessarily mandatory.

She got four A’s in her GCSEs
“Mississippi” has four i’s and four s’s
They decided to play X’s and O’s (or “Xs and Os”)
We were taught the three R’s (or “three Rs”)

A final point: like pluralised abbreviations, decades and centuries written as numerals once commonly ended in apostrophe-s: 1800’s, 1960’s. Nowadays, however, the apostrophe tends to be left out: 1800s, 1960s. The same goes for abbreviated decades: ‘60s, not 60’s or ‘60’s. This trend pleases me.

26 Responses to Plurals of acronyms, abbreviations, initialisms and single letters

  1. Grandad says:

    Regarding your search for WMDs (didn’t I read somewhere that someone else was looking for them too?) would it not be pedantically correct to state WsMD? After all, it is the Weapon that is plural, and not the Destruction?

    On a slightly different tack, I am often amused by the use of such very common expressions such as “ATM machine” which doubles up on the “machine” or “PIN number” – Personal Identification Number number?

  2. Vero says:

    Great post! I’m guessing that the high school students who were studying for their SATs got better SAT results than the ones who were studying for their “SAT’s”. :-)

  3. Stan says:

    Grandad: Yes, I have a feeling I wasn’t the first to go looking for them, but I wonder if anyone else thought to search for them there. And what would I have done had I found them? Abbreviated redundancies amuse me too. I hear your examples quite a lot, and there’s also the CPI index, RSVP please, UPC codes, the HIV virus, etc. There’s an impressive collection of these RAP phrases (Redundant Acronym Phrase phrases) here.

    ‘would it not be pedantically correct to state WsMD?’

    I see what you mean, but I think that would be hypercorrection. When words and phrases get initialised, the initials don’t retain strict one-to-one correspondence with the words they refer to, and we pronounce the letters rather than treat them as words. So an initialism becomes a new entity, a noun in its own right, demanding -s at the end of its plural like most of its neighbours have. Some plural compound nouns have an internal -s-, e.g. mothers-in-law, but if this was commonly initialised we would still say “em-eye-elz” rather than “emz-eye-el”.

    Vero: Thank you! Perhaps you’re right, but it would depend on a lot of known and unknown unknowns. How the papers are marked, for example.

  4. Kellie says:

    Funny enough, I was explaining this to a friend just a few days ago. She was having a hell of a time trying to make “The B-52s” possessive, in particular because only recently did the band drop the unnecessary apostrophe. (They were The B-52’s for decades.) I don’t agree with all stylistic conventions (much as I understand the rationale, I just cannot get on board with capitalizing “website”/”web site”), but I’m relieved to see that extraneous apostrophe finally falling out of vogue.

  5. Stan says:

    Kellie: My sister was singing something to the tune of “Love Shack” over the weekend. She knew the melody but not the band, and I had no idea about the change to their name. Thanks! But will Therapy? ever drop that infernal question mark?

    “Falling out of vogue” is a good way to put it: we’re talking style, after all! There appear to be conflicting conventions on the capitalisation of website. (I don’t either.) A related one is whether or not to hyphenate email, though this seems less contentious. Occasionally I do; usually I don’t.

  6. Sean Jeating says:

    Same phenomenon in German(y), Stan; and this goes for Grandad’s examples, too. One more: Not that Germans would send respectively receive a short message (sm), no, they would always send / receive the whole short message system (sms).
    Enjoyed reading this very much. Thank you.

  7. Fran says:

    Great post. I’m so glad there are still people fighting for this one. I think English teachers as a general rule have given up, and even my sixth formers are shocked if I correct their work this way!

  8. E says:

    “Upper case letters are clearer: Mind your Ps and Qs. But this increase in clarity can be negligible: Dot your Is.”

    I prefer the capitalization method, just so it doesn’t perpetuate the myth that ‘s makes a plural. I’d rather err on the side of omitting ‘ when it’s necessary rather than add fuel to the wrong fire. As you state, “Unnecessarily apostrophised plurals, as well as being unsightly, almost certainly increase general confusion about plural formation.” Amen.

  9. Kellie says:

    But will Therapy? ever drop that infernal question mark?

    Haha. Honestly. One of my favorite bands is called Suddenly, Tammy! — which never fails to generate ridiculous-looking sentences.

    There appear to be conflicting conventions on the capitalisation of website. (I don’t either.) A related one is whether or not to hyphenate email, though this seems less contentious. Occasionally I do; usually I don’t.

    I must admit: “E-mail” is another pet peeve of mine, though again, I do understand the rationale. Net functionality has become so commonplace that I think it makes far more sense to send an email about an interesting website than an E-mail about an interesting Web site. The latter feels too 1993.

  10. Claudia says:

    When, at 24, I bravely plunged into full time English, barely knowing the basics, I would have gone back to my safe French corner, had I seen all the problems I could encounter with apostrophised plurals. Sometimes, ignorance is bliss! I trusted my eyes, my ears, my instinct and people’s indulgence. For me, from the beginning, it was very simple. Apostrophe‘s meant possession, “My mothers’s dress.” A lone s meant plural, “The 30s”. It looked good that way. It still does! Reading your interesting post gave me comfort. I might have missed a few times, but not as often as it could have been.

    Redundancies happen a lot in bilingual Canada. It was amusing to hear that my friend’s son was a head chef. I thought, “Better to have two than none!”

  11. Claudia says:

    Stan – I put an extra s to mother. I only had one really. Otherwise, it would have been dresses. Typo’s mistake. If there are others, please, let me know. Thank you.

  12. […] here to see the original: Plurals of acronyms, abbreviations, initialisms and single letters « Sentence first Share and […]

  13. Stan says:

    Sean: As is often the case with language, habit overrides sense! I’m glad you enjoyed the read.

    Fran: Thank you. I am shocked that your sixth formers are shocked! Apostrophised plurals must be even more prevalent than I suspected. As I remarked elsewhere (today’s euphemism for Twitter), the trouble is that it’s a convention (with exceptions) rather than a rule, and a little confusion leads to a lot.

    E: Thank you for your comment. I sympathise with your position, but I like to keep my options open when I reasonably may. For example, if I want to make a distinction between upper- and lower-case letters, then using upper and lower cases may be the most natural way to do this. I don’t want to deny myself that option in order to avoid the possibility that others will see a rule where there is only an exception to a convention! Everyone’s usage is their own responsibility. But there are reasonable arguments for various approaches, and a great deal depends on context, judgement and taste.

    Kellie: This chat has reminded me of a few more: NEU! (apparently they always used capitals), Sunn O))), Godspeed You! Black Emperor (the exclamation used to go at the end), …And You Will Know Us By The Trail Of Dead, and Sh-Sh-Sh Shark Attack!!!. Googling “band names punctuation” I soon found a list that includes a band called !!!. Also known as Chk Chk Chk. Hmm. My preference is definitely for email, but if I’m editing text with e-mail I generally leave the hyphen be. The capital E has to go, though.

    Claudia: Trust me, you write beautifully. An occasional slip, inevitably, but even native speakers succumb to those. I’m very glad you didn’t abandon English! (Apart from the extra s, your comment is fine.) The simple guideline you mention is mostly valid, but the trouble is that it smudges at the edges, and there are always exceptions. I suspect that one of the chief reasons for the its-it’s confusion is that people think to themselves “apostrophe-s means possession” – it usually does – and they might then write “it’s tail was wagging [sic]”.

  14. Tim says:

    English is a language that is full of special rules and exceptions. ^^ Like the example you just gave in that last comment there, about it’s and its. Because we use the apostrophe form for both possession and as an abbreviation of “is”, I can see how it could be confusing for both non-native speakers learning our language and for those who never grasped simple grammar rules at high school.

    What I really wanted to say, however, is that the article was a good read. And it reminded me of how annoying it is to see people pluralise with apostrophes — especially on signs. It always makes the back of my brain itch because of how unnecessary (and ultimately confusing) it is to do so.

    I also have a question regarding acronyms: Is it imperative to write (common) acronyms with capital letters or is this just a convention? I often write lol rather than LOL, or dvds rather than DVDs. I always saw it as a choice; especially when the acronym is so well known that there can be no confusion, even when pluralised.

  15. Stan says:

    Thanks for your comments, Tim. I suspect that many people who did grasp the its-it’s rule in school have since forgotten it. I see the mistake made regularly even by good writers. Yet it’s not a difficult distinction to make and remember. Maybe I’ll dedicate a blog post to it after all.

    Regarding capitalisation of acronyms and initialisms, conventions vary. Some stay capitalised everywhere, e.g. WASP, IRA; some are now so common that they’re barely recognisable as acronyms, e.g. laser, radar. Publishing house styles differ. For example, full capitalisation tends to be retained in America more than in Britain, at least according to Bryan Garner.

    There is a tendency for many true acronyms to be written first in upper case with full stops, then in upper case without full stops, then in lower case (or lower case with an initial capital): U.N.E.S.C.O. → UNESCO → Unesco; A.I.D.S → AIDS → Aids. The Oxford Manual of Style recommends the single-initial-capital form for proper-name acronyms longer than four letters (e.g. Basic, Unicef, Unesco), but says that editors should avoid this rule “where the result runs against the common practice of a discipline” (e.g. WYSIWYG).

    Strictly speaking, DVD is not an acronym but an initialism (though the distinction is not always made). You’re right that some such terms are familiar enough to preclude confusion – certainly in most contexts – so in informal writing you should do as you please, as long as your meaning is clear. Occasionally I write dvd, but I usually retain the capitals. I try to avoid LOL in any form!

  16. Kellie says:

    I soon found a list that includes a band called !!!. Also known as Chk Chk Chk.

    Rather than vocalize the name, I think I would simply bug my eyes wide and tense my neck and jaw every time I needed to refer to !!!. (I can’t help but perform a serpentine dance when referring to the artist formerly known as Prince either.)

    Thanks for the link to the punctuation bands. I’m curious to know what What The…? sounds like.

  17. Great article.

    George Vreeland Hill

  18. ana says:

    I’m so glad I’ve stumbled across your site. I’m doing some research of my own (need to know how to pluralise POI for a translation). I was in two minds about whether to leave it as it is (e.g. “these POI”) or to treat it like MP (e.g. “these MPs”). After reading your article, I think I’m just going to treat it like MP.

  19. Johannes Schade says:

    Nice and amusing site! I came across an initialism TOR for ‘terms of reference’. Then I found a request for proposals by the World Bank where the terms of reference were called the TORs.
    Should I write “the TOR says” or “the TORs say”?

    • Stan Carey says:

      Thanks, Johannes. The usual style for pluralising initialisms is to add a lowercase ‘s’, hence ‘the TORs say’.

      • Johannes Schade says:

        Surely, yes. Sorry, I should have explained better. The cited text introduces the acronym (I wrongly call it an initialism as we pronounce it /tɔ:/) saying “Terms of Reference (TORs)”. I had some time to think better about it and now think that one should reject such a definition. An acronym or initialism should be defined by a suite of uppercase letters taken from the initial letters of the words of the term to be abbreviated.Terms of Reference should therefore be “acronymed” as TOR and not as TORs, even if Terms is in the plural. Do you agree?

      • Stan Carey says:

        No. The usual convention is to add a lowercase s when pluralising an acronym or initialism, hence TORs, etc. This is the style recommended by the Oxford Manual of Style, the Chicago Manual of Style, and Merriam-Webster, among others.

  20. Shell says:

    I am also amazed at how we deal with plurals that come from Greek, such as loci and locus. “Quantitative Trait Locus” is abbreviated QTL. When we need the plural, which is “Quantitative Trait Loci”, should it be QTL, or QTLs? I see more frequently QTLs,

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