The Many Forms of Plurals

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Plurals take many (sometimes curious or counterintuitive) forms. Here is an outline of how to form various types of plurals according to the word form or ending:

For words ending in

  • nonsibilant, or voiceless, consonants: add -s (dogs)
  • voiced, or sibilant, consonant blends: add -es (riches)
  • vowels: add -s (knees)
  • -f: delete -f and add -ves (loaves) or -s (chiefs)
  • -x: add -es (foxes)
  • -y: delete -y and add -ies (bodies).

For words of Latin or Greek origin ending in

  • -a: add -s or -e, depending on context (formulas/formulae)
  • -ex: add -es or delete -x and add -ces, depending on context (indexes/indices)
  • -ies: leave as is (species)
  • -is: change to -es (axes)
  • -ma: add -s or -ata, depending on context (stigmas/stigmata)
  • -um: add -s (aquariums), delete -um and add -a (curricula), or either depending on context (mediums/media)
  • -us: delete -us and add -i (alumni), -ii (radii), -era (genera), or -ora (corpora), or leave -us and add -es (octopuses) or use another form, depending on context (cactuses/cacti).

Types of irregular forms include

  • ablaut, or mutated, plurals, with changes in the midst of a word (teeth, lice)
  • identical singular and plural forms (deer, spacecraft)
  • -en and -ren endings (oxen, children).

Some words have more than one plural form, one of which may be archaic (cows/kine) or reserved for a distinct meaning (dice/dies).

One problematic category is in referring to fish in general and specific varieties of fish in particular: “Look at all the fish!” but “Gars are long, slender, predatory fishes.” Also, some types are given a distinct plural form (sharks, barracudas), though for others, the plural form is identical to the singular one (salmon, sturgeon).

Plurals of letters, numbers, or abbreviations are generally formed simply by adding -s, although occasionally, the otherwise incorrect use of an interceding apostrophe is warranted (“Mind your p’s and q’s”). Usually, however, pluralizing names of letters requires no special treatment, especially when the letter is italicized, as here: “There are five es in beekeeper.” Initialisms and acronyms also usually require only an -s: “Many NGOs are headquartered here,” “It’s like having two NASAs.” (An exception is made when the last letter is an s, as in CMSes.)

The singular forms of some words are, because they end in -s, sometimes mistaken as plurals, and the letter is then incorrectly deleted to create a false singular form. Examples include gyros, kudos, and biceps (as well as triceps and quadriceps). The plural forms are the same, although the latter examples are alternatively (and rarely) pluralized by adding -es. For other words, the original singular has been supplanted by a plural form used in both cases (alga by algae; graffito by graffiti).

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20 thoughts on “The Many Forms of Plurals”

  1. Interesting stuff. You missed out the words of Greek origin ending in -on, which take a plural in -a: eg criterion/criteria, phenomenon/phenomena. I see these used wrongly quite often.

  2. By the way, I don’t see what’s wrong with “Mind your Ps and Qs”, which avoids the need for those ugly apostrophes.

  3. In the -us item, your example for adding -ii is in error. For radius, the -us is deleted and it retains one -i, so only one additional is added.

    Also, for “… five es in …”, ought the e be italicized in “es”?

  4. ‘One problematic category is in referring to fish in general and specific varieties of fish in particular: “Look at all the fish!” but “Gars are long, slender, predatory fishes.” ‘

    I think it’s the other way round — fishes for more than one species, fish for a single species. So:

    ‘One problematic category is in referring to fishes in general and specific varieties of fish in particular: “Look at all the fishes!” but “Gars are long, slender, predatory fish.”’

  5. I agree with Michael re: using capital letters to denote the name of the letter – it just reads more clearly.

    Re: dice. I always thought it was one die, many dice… or has that now been classified as archaic?

  6. And all this time I thought a group of Elvis Presley impersonators would be “Elvi” or maybe “Elvises.” But apparently they are “Elves.” Hmmmm. Not sure I can convert!

    I would write the “es” as “Es” or even use another construction, such as: The letter e appears five times in beekeeper.

    I do agree with Michael about the Ps and Qs. I don’t like apostrophes that aren’t replacing letters (as in contractions) or indicating possession. It’s a plural and to me, plurals don’t get apostrophes!

  7. Just wanted to second the comment about radius only having one i added for the plural form, as the other i is already in the word. Great post though.

  8. don’t forget that a few ‘f’s’ do not take the ‘ves’ form – roof – plural form is roofs.

  9. Actually, I disagree with your explanation for knowing whether plurals end in -s or -es based on whether they are behind a voiced or unvoiced consonant. First of all, in your example “dogs”, the /g/ is a voiced consonant. (It’s unvoiced equivalent is /k/.) I think whether it is -s or -es depends on which part of the mouth is making the final consonant and how it is articulated: since /s/ and /z/ are both alveolar fricatives, meaning the tongue is placed on the alveolar ridge between the front teeth and the hard palate and the sound is created by pushing the air through a narrow channel (in this case that between the tongue and teeth). /ch/, /sh/, and both “j” sounds are all either fricatives or affricates (consonants that begin with a sound like /d/ or /t/ and end in a fricative) AND they are post-alveolar, meaning they are produced by putting the tongue at the back of the alveolar ridge. Since it is difficult to produce two very similar sounds in quick succession and have them still be distinct, we add a short vowel sound (represented by an “e”) in between the two consonants. Thus, any word that ends in /ch/, /sh/, /s/, /z/, or either “j” sound (all alveolar or post-alveolar, and fricative or affricate) is made plural by adding an -es to the end. If you ever need to know which to do and can’t remember the list of affected sounds, just remember that if it’s difficult to say when you add just an /s/ or /z/ sound and it doesn’t sound very clear, you probably need to put an “e” in front of the “s”.

    Also worth noting is the fact that in words ending in the unvoiced “th” sound (such as “moth”), the final sound is usually changed to a voiced “th” such as the one in “the”: “moths”. (This is another reason why Americans are uncomfortable with “maths” instead of “math” as the abbreviation for “mathematics”; it just doesn’t sound quite like an English word to us.)

  10. These “rules” aren’t very useful; especially for Latin/Greek words, they’re more likely wrong than right (you need to know which declension the word follows, and sometimes the gender; what letters it ends with doesn’t give you that. FWIW, the proper plural of “octopus” is “octopodes”). Also need to add Semitic plurals in -im, etc.

    Also worth noting is the fact that in words ending in the unvoiced “th” sound (such as “moth”), the final sound is usually changed to a voiced “th” such as the one in “the”: “moths”.

    Sounds like some sort of speech impediment. I pronounce “moths” exactly like “moth” (except for the final /s/).

  11. Also worth noting is the fact that in words ending in the unvoiced “th” sound (such as “moth”), the final sound is usually changed to a voiced “th” such as the one in “the”: “moths”.

    Can you distinguish between “thistle” and “this’ll”?

  12. Of course you can distinguish between the sounds, but for some reason or another in at least some dialects of English the unvoiced “th” is often changed to a voiced “th” when immediately followed by an /s/ or /z/ without any vowel in between. I realized that it’s actually the same principle as changing an /f/ to a /v/ when making some words plural that have a final /f/, since /v/ is the voiced form of /f/. The /f/ and /v/ sounds, and both “th” sounds, are all fricatives (though this time they use the lips and teeth) and maybe it’s natural for us to change the unvoiced fricatives to a voiced one when followed by an /s/ or /z/ sound with no vowel in between. Obviously you speak a slightly different dialect of English than I do to not change the unvoiced “th” to a voiced one. And I don’t have any sort of speech impediment, so I don’t appreciate your comment suggesting that. Your accent is not the authoritative one, and my accent does not involve a speech impediment.

  13. I also thought it was pretty clear that my rule about changing some unvoiced sounds to voiced ones ONLY applied when they were immediately followed by an /s/ or /z/ sound; of course I pronounce “thistle” and “this’ll” differently. In fact, I admit that not every word that ends in the unvoiced “th” or /f/ will have the consonant change, but that SOME will, but that obviously in whatever Western American dialect I speak more words than not DO have the consonant change, and that that most other English dialects seems to have a similar, though not identical, pattern. (For example, someone else commented that the correct plural for “roof” is “roofs”, while I would say that to me the correct plural is “rooves”, at least in pronunciation.)

    In regards to “medium/media”, I would say that media (at least in the context of visual art) is not a singular word, but that it is always “medium”, and that the plural can be either “media” or “mediums” (though “media” is more common). I couldn’t speak for other fields, though, or even all other artists, but this is the way I usually hear it used.

  14. Am I the only one here who works out? There are singular forms for the muscles … bicep – … According to M-W ( and the dictionary on my computer … bicep is singular and biceps is plural.

    And if you go to the gym, it’s bicep/biceps. Common usage usually wins out over neo-Latin hybrids. Even in English, we wouldn’t say “two-heads muscles”.

    As for radius:
    radius |rādēəs|noun (pl. radii |ˈrādēˌī|or radiuses) …

    Let me consult my medium about media? Hmmmm, she says when one brings in foreign words that we apply English rules to them … but that there are always a few latin-philes who keep on using the Latin plurals … and that media is a collective noun and it’s ok to use a singular verb with it (same for data).

    And then there is Toyota with their completely screwed up plural for the Prius! They did it by vote and the ironic thing was that the proper Latin plural wasn’t even a choice. LMAO!

    spacecraft |spāsˌkraft| noun (pl. same or -crafts)

    gyro 1 |jīrō| noun (pl. -ros)
    short for gyroscope or gyrocompass .
    gyro 2 |yērō; zh irō|
    noun ( pl. -ros)
    a sandwich made with slices of spiced meat cooked on a spit, served with salad in pita bread.

    Either way … it is gyro – gyros.

    Kudos is the only one in that group that definitely has no singular form … as far as I know.

    I agree with Keith … sounds to me like you have the fish-fishes byspel backwards.

  15. Stick to your guns Emma and other Emmae. The rules you refer to are generally correct for American, anyway. Seems like some of the problems here just stem from a lack of understanding that national standards differ. You can say, “In American English it’s spelled color”, and invariabley someone will reply, “I don’t think that’s right. I’m from Worcestistashastashistashire (pronounced Wussa) and we spell it colour.”

    Even bigger problems arise from those that just don’t believe there are any standards at all for these things. Or the standard is just whatever most people say. Most people don’t know data is plural? Oh, then it’s not plural. I guess just declaring wrong right is cheaper than educating people. I hope they arent adopting that standard for airplanes and bridges.

    For example, from the online dictionary (not exactly pedantic):
    -ceps comb. form of caput “head” (see head). Despite the -s it is singular, and classicists insist there is no such word as bicep.
    I don’t know about classicists, but as a normally educated person, I knew this already. Is this really difficult?

  16. These “rules” aren’t very useful; especially for Latin/Greek words, they’re more likely wrong than right

    You have a point, but a limited one. Regardless of how plurals were actually formed in Greek or Latin (declensions? Are you serious? lol)
    conventions have formed in various arenas regarding how the “pseudo-Latin/Greek” plurals are formed for terms of art. In mathematics, e.g., the plural of formula is formulae, among zoologists 2 or more are octopi. Among normal people they are, of course, formulas and octopuses. No need to go wildly romanizing words that have been English for so many anni, annis…pardon while I declent…annos, annorum…

  17. This is odd. First:

    Also worth noting is the fact that in words ending in the unvoiced “th” sound (such as “moth”), the final sound is usually changed to a voiced “th”


    Can you distinguish between “thistle” and “this’ll”?

    Well, yeah. Can you distinguish between word endings and word beginnings? Weird.

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