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Between "Us" and "I": Getting Stuck on Plurals

The editors were discussing a story about the health benefits of a particular type of cactus, and maybe others. The story was called "Cacti." "Is it cactuses or cacti?" one asked. "The plural of cactus is cactuses," another said, adding wryly: "Is the plural of circus circi?"

Yes, another Latinate ending that made it into some English words, but not others. And, sad to say, there's no easy trick to which ones are pluralized by changing the "-us" to an "i" and which ones get the "es" treatment.

For some of the words, there is no debate. The plural of "circus" is "circuses," not "circi." The plural of "alumnus" is "alumni," not "alumnuses." The plural of "campus" is "campuses," not "campi."

But the "cactus" question is a prickly one. Dictionaries differ on which plural they prefer, though they list both. Webster's New World College Dictionary likes "cactuses," while American Heritage and Merriam-Webster go with "cacti." Therefore either is correct. (M-W says "cactus" is also an acceptable plural.) Your choice may also depend on context: If you are speaking of the plants from a botanist's view, "cacti" is preferred.

Another disarming "-us" word is "octopus." Its plural could be "octopuses" or "octopi." Most dictionaries prefer "octopuses"; some linguists sniff at "octopi" as "hypercorrection," used by people who bend so far backward trying to be faithful to supposed rules of grammar that they fall over. "Octopi," though, is quite common in print: It has made dozens of appearances in The New York Times, for example, even though The Times stylebook wants "octopuses."

Other plural forms of "octopus" that have been used are "octopod" or "octopodes." An "octopod" is any creature with eight limbs, including an "octopus," so that won't fly. Showing how language evolves, Webster's New International Dictionary, which ruled from 1909 to 1961, listed "octopodes" as second choice for plural. Nowadays a few dictionaries still list "octopodes" with "octopus," but as a variant and singular. The plurals, they say, are (in order of preference) our friends "octopuses" and "octopi," and also "octopodes."

In a multipage entry on plurals, Garner's Modern American Usage seems to throw up its metaphorical hands on how to pluralize "-us" words. In essence, it says that if a word "imported" from another language has been "naturalized," it takes the plain-vanilla plural ("s" for most words, "es" for most ending in "s" or "z"). "But if a word of Latin or Greek origin is relatively rare in English — or if the foreign plural became established in English long ago — then it typically takes its foreign plural."

So who determines whether a word is "relatively rare" or "became established in English long ago"? Why, you do, of course. How people use words determines whether they are "correct." The more people use them, the more "correct" they become.

Then there is "virus." When it started taking hold as the description for a software program that makes a computer do things it shouldn't, some programmers, known for having fun in the naming of new things, apparently decided that the plural "viruses" was boring. Instead, for a few years into the mid-2000s, the plural was occasionally "viri" or "virii." Thankfully, that disease seems to have run its course, and "viruses" prevails, except in mocking contexts.

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Merrill Perlman is adjunct assistant professor at the Columbia Graduate School of Journalism and president of Merrill Perlman Consulting, offering consulting and freelance editing services and training in journalism, grammar and usage. Among her clients are The New York Times, ProPublica and the Poynter Institute. She writes the "Language Corner" column and blog for Columbia Journalism Review. Merrill retired in June 2008 after 25 years at The New York Times, most recently as director of copy desks with responsibility for managing 150 copy editors. Click here to read more articles by Merrill Perlman.

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Comments from our users:

Wednesday August 14th 2013, 10:46 AM
Comment by: Suroor A.
It's the same problem with words like forum--is the plural forums or fora? My last workplace used the latter and the one I work in now uses the former. Just to confuse things!
Wednesday August 14th 2013, 1:52 PM
Comment by: Marina P.
Same thing with "platypus" (my small business is called "Platypus Studio" and I am asked every now and then what the plural form of "platypus" is. I answer "platypus". Platypus has a greek root, and the "i" comes from Latin roots, I believe. Am I wrong?
Wednesday August 14th 2013, 3:26 PM
Comment by: William H. (Severn, MD)
I frequently read and write about firefighting topics. Firefighters commonly refer to their various types of trucks as "apparatus." My American Heritage dictionary gives the plurals as "apparatus" or "apparatuses." Most often, "apparatus" is used as the plural, but a recent news site used "apparatuses," which, although correct, looked strange. Where practical I try to rewrite the sentence to avoid the plural.
Wednesday August 14th 2013, 4:26 PM
Comment by: Westy (Paris, OH)
All this happens just after some other scholar convinced me that the Greek plural of octopus is octopedes.
Wednesday August 14th 2013, 4:41 PM
Comment by: mark M. (NJ)
Have to smile about root words and where they evolved from! Take fibromyalgia, if that is the correct spelling. Those who decided to create something in thought or mind decided to make up a word and write a paper about it. The paper was put away and then 14 years later it was made manifest and has become very real! How dicombobblating, it is!
Wednesday August 14th 2013, 5:45 PM
Comment by: Mark K. (New York city, NY)
Use your words to say exactly what you mean.
Thursday August 15th 2013, 12:15 AM
Comment by: Frederick E.
Merrill, U are a Star. keep digging at them roots (plural)
Thursday August 15th 2013, 5:47 AM
Comment by: Nick Shepherd (London United Kingdom of Great Britain and Northern Ireland)
Being in education In London (UK), the two I struggle with are syllabus (I prefer syllabuses) and curriculum (I think you have to say curricula, but I'm umming and ahing about that one).

Agenda is easy: it's technically plural, but we have now firmly made it singular, at least in the UK.

And you don't mention that horror, data. What kind of a word is data? Is it plural uncountable? And do we use datum for one bit of information? I don't, myself; it feels awkward.

Time for another article, Merrill?

Nick Shepherd
Juggling with English
Friday August 16th 2013, 6:19 AM
Comment by: keith M. (Kula, HI)
And speaking of plurals, lets be clear about the mongoose. Though it's tempting to go with mongeese, it is really is mongooses. And similarly there is one moose, and two mooses. Keith Mac in Kula, HI
Saturday August 17th 2013, 12:42 PM
Comment by: Susan C.
As someone who drives a Prius (pl. = Prii according to Toyota, seriously), I can relate to how tangled the rules of pluralization have become. Prii actually got 25% of the votes when Toyota opened up the naming campaign to the public. I thought it was stupid at first; now it's just fun to say.

P.S. I've never seen "fora" used as the plural of forum. Just bizarre. But mongeese sounds great. Think I'll start going with whatever sounds good to me. And then wink.

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