When to Form a Plural with an Apostrophe

By Maeve Maddox

This reader wants to know why we write 1980s and not 1980’s.

I understood that making text entities with non-letter characters into a plural form, you separate the s from the term with an apostrophe – 1900’s, Jones’, Smith’s, or Bang!’s.  So, why no apostrophe with 1980s?

A lot of writers share this reader’s understanding that non-letter characters are pluralized by adding apostrophe s.


Alas, indeed. That pesky apostrophe raises a lot of blood pressure for writers of English.

If I had my druthers, we’d phase out altogether the use the apostrophe to form the possessive of nouns. What meaning would be lost if we wrote my mothers birthday, the cats tail or the cats tails?

Teachers and editors could save their red ink for dealing with the apostrophe and plurals.

NOTE: I’ve received so many protests regarding these facetious remarks that I hereby withdraw them. We do need the apostrophe to form the possessive. Mea culpa, dear readers.

I can’t really answer the reader’s question. What I can do is lay out what the Chicago Manual of Style says about when to use an apostrophe and when not to. And it has a lot to say. Here are only some of the rules this style guide offers.

Don’t use an apostrophe to pluralize a proper name or other capitalized noun:
Many Pakistanis have immigrated to the U.S. (not Pakistani’s)
I’ll be occupied for the next three Thursdays. (not Thursday’s)
The Jeffersons live here. (not the Jefferson’s)

NOTE: The CMS suggests that if you want to pluralize an awkward name like Waters or Rogers, you may want to reword the sentence to avoid writing the Waterses or Rogerses. (or Maddoxes?)

Don’t use an apostrophe to pluralize a title:
I have three Madame Bovarys and five Animal Farms. (Type the title in italics and the s in Roman face.

When forming the plural of words and hyphenated phrases that aren’t nouns but are used as nouns sometimes you do and sometimes you don’t:
I want no ifs or buts.
Here are the dos and don’ts of blogging.
I’ve written 25 thank-yous.
I’m tired of all his maybe’s.

DO NOT use an apostrophe to form the plural of capital letters used as words, abbreviations that contain no interior periods, and numerals used as nouns:
the three Rs.
the 1990s
lengthy URLs

NOTE: For the abbreviations p. (page), n. (note), and MS (manuscript), the plurals are pp., nn., and MSS

And for you scientific types, special rules apply for the plural of SI symbols:

No periods are used after any of the SI symbols for units, and the same symbols are used for both the singular and the plural. Most symbols are lowercased; exceptions are those that stand for units derived from proper names (A for ampere, etc.) and those that must be distinguished from similar lowercased forms. All units are lowercased in their spelled-out form except for degree Celsius (°C).

For those of you who, like me, hadn’t heard of SI symbols, you’ll find a list here.

DO use the apostrophe to form the plural of an abbreviation that combines upper and lowercase letters or has interior periods:
The department graduated five M.A.’s and two Ph.D.’s this year.

NOTE: If you leave out the periods, you can write MAs but you’d still have to write PhD’s.

DO use the apostrophe to form the plural of lowercase letters:
Mind your p’s and q’s.

DO NOT use the apostrophe to form the plural of capital letters:
What the CMS actually says is
Capital letters do not normally require an apostrophe in the plural.

One could write a sentence like this without confusing a reader:
You need to improve the formation of your Ts and Zs.

But one might be tempted to reach for the apostrophes with a sentence like this:
You need to improve the formation of your Ss, Is, and Us.

And finally—DRUM ROLL–our reader’s question about using an apostrophe with non-letter characters:

DO NOT use an apostrophe to form the plural of a number:
The 1920s were noted for excess.
I bowled two 300s and two 238s.

Source: Chicago Manual of Style, paragraphs 7.9, 7.12, 7,14, 7.15, 7.16, 7.65, 9.59.

55 Responses to “When to Form a Plural with an Apostrophe”

  • Ned G

    Swedish forms its possessives without apostrophes and that works out just fine. Their plural suffix is -ar (generally), though, so it doesn’t present any potential ambiguity with their possessive suffix (-s, like us).

  • Bryan W

    We most definitely need apostrophes to form possessives 🙂

    “My roommates cars bumper stickers highlight my favorite political groups quotes.”

    How many roommates? How many cars? How many political groups?

  • Maeve

    I’d say that letter grades would take an apostrophe to avoid this kind of thing mentioned in the post:

    “But one might be tempted to reach for the apostrophes with a sentence like this:
    You need to improve the formation of your Ss, Is, and Us.”

    The plural of the letter A without an apostrophe would look like a word: Susan received five As and a B).

  • Michael Stranathan, M.A.

    What about letter grades? By designating a grade with a letter you are assigning a name and capitalization of the name requires use of an apostrophe when one is talking about more than one grade (e.g., Susan received five A’s and a B).

  • Jonathan Leung

    Though not about pluralization, there are two points about apostrophes I’m also curious about:

    I’ve often seen people write “I would of”, which is ridiculous, because clearly they mean “I would have”, or shortened, “I would’ve”. But when it’s in the negative, is it “I wouldn’t’ve”? I use that a lot because that’s how we say it, but how often in English should there be multiple apostrophes in one word (or one contracted word)? (And lo, spellcheck proves my point by underlining “wouldn’t’ve” with a red line…)

    And then there’s “you’re”, which is obviously “you are”. (Well, it should be obvious, but that’s another point.) But what about at the end of a sentence? If someone says “you are what you are”, it looks weird to me to say “You’re what you’re”. I’m not sure that I’ve ever heard the rule that some contractions can’t end a sentence; is there one?

  • Jonathan Leung

    Little surprised you’ve never heard of SI units…? How do you measure things? Even if you live in the United States which hasn’t adopted the metric system for most things I’m pretty sure kilobytes and megabytes must be common usage, aren’t they?

    Anyway, and I could be being difficult here, but what if you had an art project, like an image or sculpture, that involved the letter “S” repeated, and the big ones were made of multiple ones? So if you were commenting on them, would you refer to “the letter Ss’ Ss?” Or “the letter Ses’ Ses?”

    This is something I’ve wondered about for a while, and now that I scroll up I do see that Lisa asked the same thing back in June, at least about plural S. “Ses” makes sense but looks like it could be easily mispronounced “sess”.

  • Joris van den Outenaar

    In Dutch, we form possessive nouns by only attaching an S. Funnily enough, people still (erroneously) add an apostrophe sometimes. Perhaps they picked this up from reading English. Perhaps they just write down whatever fancies them.

    My guess is you won’t get rid of spelling mistakes by transitioning to a seemingly easier system.

  • Kiwi-Ian

    Ms Foster – I’m with you. If you never use an apostrophe in a plural you will never be wrong. There maybe a few instances where grammarians may accept an apostrophe, but I think that for the vast majority of cases, no apostrophe = right (or least not wrong).

    Scott Snyder – I’m with you too. One says Charlzez book so one should write Charles’s book.

    Trevor Hansen – it would be interesting to know if these letters from the mid 20th century referred to a plural or a possessive, e.g., “went to the Adams’s last night for dinner” actually refers to the Adams’s home, just as you would say “I went to John’s [house] last night”.

    Jon – I wonder whether the rules have changed or whether your teacher was from a generation which was trying to relax the rules (confusingly). I have an English Ladies’ Encyclopedia from 1928 which essentially agrees with with what I have said above.

    There are times when perhaps rephrasing is the best policy. Other languages do this all the time.

    If you think English is complicated try learning another language. Spanish and French have 4 and German 6 ways of saying “the”! The most irregular verb in English (to be) has just 8 forms (be, been, being, am, are, is, was, were), a regular French verb has at least 32 and an irregular one (être = to be) is approaching 50.

    Perhaps our worries about the use of the apostrophe are because English grammar is so easy and usually intuitive that it is no longer taught in schools and trivial problems become big ones. Just remember, we only have 1 form of “the” and 2 ways of saying it depending on the following letter.

  • Erick

    Lisa: Your question was answered in multiple comments.


    And in your sentence, it would be “There’re” or “There are” as you are referring to multiple S’s.

  • Lisa

    Here is the sentence that I have to type:

    There’s a lot of S’s in that acronym.

    Is it S’s or Ss or Ses? My inclination is to go with the first one so that the reader better understands the sentence.

  • Lane Elms

    What about a model number that includes letters and numbers? I often refer to loudspeakers with model numbers like JF80, UPM-1p, or UB40e. Sometimes an “s” at the end could change the meaning of the model number. Could I use an apostrophe if that was the case without looking like an idiot? UPA-1P’s, JF80’s, etc.

  • Amelia

    This is nonsense:
    “NOTE: If you leave out the periods, you can write MAs but you’d still have to write PhD’s.”

    PhDs is perfectly understandable.

  • Steve Loh

    What if my students all just got As? Or should it be, they all got A’s? I know the rule, but the second way sure seems to be less confusing. If a college student received five semester grades, all As, that seems unclear. But all A’s — that seems better. And three A-s seems like I’m trying not to write the word Ass. Help!

  • David

    “What is the plural form of the grades A-, A+, B+, etc.?”

    I’ll give it a shot: If a subset of students all received the same grade on their reports, then the grade need not be pluralized. There is only ONE grade, A-. You don’t need to say “They all received A minuses or As minus on their reports”, you just say “They all received A minus”.

  • Daniel

    Well, I kind of like the apostrophe. Although I must say, many of the rules above are entirely arbitrary. I am pro-apostrophe as long as it makes sense.

    Here are some cases in which I think it makes sense, some contrary to the CMS:

    -Capital Letters: I think Z’s and S’s look much nicer anyway, and in cases like the ones given in the article it definitely improves clarity. So why not just do it for all? No confusion that way, just think of the cases that necessitate it if you ever forget! (Also it’s consistent with lower case letters. I cannot fathom why on earth it would make sense to use two different rules for lower- and uppercase letters here.)

    -Numbers: I think numbers (numerals) make sense to use apostrophe plurals for as well. With the technological developments of recent times, naming schemes that produce names such as “iPhone 4s” have become prominent. This is not the “iPhone ‘fours'”. I think there are very, very few cases in which the apostrophe causes any confusion in the pluralization of numerals.

    I’m still on the fence about titles. However, I think we can mostly agree that “ifs or buts” being correct renders the use of the apostrophe in “maybe’s” utterly insane (or vice versa). Of note, the spell checker for this box gives me an error for ands but not ifs or buts. o.O

  • Marina

    I agree that apostrophes should be dropped for plurals. I was reminded to be confused by this at the grocery store seeing a box of Morning O’s. “Os” might look a little odd, but so is the product name.

  • Mary



    Treating serious issues with deliberately inappropriate humor; flippant.

    Synonyms: jocose – humorous – jocular – waggish – comic – funny

  • Ms Foster

    I think it would be safest never to use an apostrophe to form a plural.

    One maybe, two maybes. What is confusing about that? How does making it “maybe’s” help? Personally, the added implication of a possession confuses my eye-brain signals even more.

    The golden rule of forming a plural in English is so simple: add an S. Leaving aside exceptions and the rules for nouns ending in O, Y or F, people seem to abandon the most basic childhood principles as adults.

    Dos and don’ts, Ps and Qs, 1980s, FAQs. How are these confusing?

    I’m starting to feel a bit hysterical here. 🙂 I plead to everyone, for the sake of consistency: when in doubt about forming a plural, add an S and move on. Never use an apostrophe to form a plural.

  • Joanne

    Came across this forum trying to get the proper way to pluralize a formal name after an adjective. Is it: Silly Conejos or Silly Conejo’s?
    Word grammer checker want to add apostrophe

  • Scott Snyder

    To Edward et al.:

    “Charles’ book” is not inarguably wrong, but I’m not sure I would say it is “indeed correct.” Strunk & White recommend “Charles’s book.” AP Style prescribes “Charles’ book.” Chicago Manual prefers the s, but indicates that “it is acceptable (especially in journalism)” to omit it.

    For my money, I’ll keep the s in “Charles’s book,” both for consistency and because I say it: “Charlzez book,” not “Charlze book.”

    On the subject at hand, I question why “dos” (as in “do’s and don’ts”) does not require an apostrophe, but “maybe’s” does.

  • Glenn

    Members’ assembly, if it’s more than one member and you want to show they “own” the assembly. 🙂

  • Lily Harwood

    Can anyone help me as this is driving me mad! What if you have multiple posessors but only one possession? As in Members Assembly (more than onr member, only one assembly) – is it Member’s Assembly or Members’ Assembly???

  • Edward G. Talbot

    To Hank:

    Thank-you for pointing this out: “names ending in s or an s sound are not required to have the second s added in possessive form.”

    That saved me having to look it up to confirm that my memory is not faulty, and “Charles’ book” is indeed correct.

  • Jon

    I think the confusion stems from the fact that grammar rules change with each new generation’s pet peeves. When I was in grammar school in the 1980s, the way I just wrote the plural of “1980” would have been considered wrong. Now it is considered correct. It’s hard to keep up with rules that change from what you were taught.

  • Hank Abelard

    To Luke S.:

    The CWS says “names ending in s or an s sound are not required to have the second s added in possessive form.”

    So, it appears that you have already lost the fight against “Charles’ book”.

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