At the 2011 Detroit Auto Show, Toyota is taking a poll to determine what the plural of "Prius" should be. It's all part of their "Prius goes plural" ad campaign, as they unveil three new Prius models. The Detroit Free Press consulted with some experts, including Visual Thesaurus editor Ben Zimmer, to get their take on how to pluralize the Latin-sounding car name.
Here's an excerpt from the Free Press article:
A vote for simplicity: Priuses
For Rachel Smydra, a special instructor of English at Oakland University, "Priuses" is what works best. Even though she acknowledged: "You're going to stumble over the words a little bit."
But some Latin scholars are irate -- iratus/irata/iratum, to be precise -- that the authentic answers aren't among Toyota's five options ["Priuses," "Prii," "Prius," "Prien," and "Prium"].
Only two correct answers
The true answer to the Prius plural question is "Priora" or "Priores," according to Nick Young, a Latin and classical studies instructor at the University of Detroit Mercy.
Ben Zimmer, "On Language" columnist for the New York Times, concluded that Priora or Prii (pronounced Pri-EE, not Pri-EYE) is the correct answer. But then he added:
"Either one seems like it's trying to force a Latin plural into that word. We're not speaking Latin. We might as well form the word the way English plurals are formed."
So, is that another vote for Priuses then?
Does it really matter?
People in the trenches -- trenchi? -- don't seem to be stressing out about this debate.
"We usually use Prii when you see more than one," said the Rev. Richard Yeager-Stiver, 33, of Grosse Pointe Woods, who owns a white 2005 Prius. "To me, I don't care what they call it. We're just excited it gets good gas mileage."
You can read the full article here. For further discussion of Prius and its pluralization, check out the discussion by Visual Thesaurus contributor Nancy Friedman on her Fritinancy blog, here and here. And see Jan Freeman's Boston Globe column on the topic from 2007, which Nancy links to.
How would you choose to pluralize "Prius"? Let us know in the comments below!

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Comments from our users:
John S (Dublin Ireland)
Language columnist Jan Freeman, writing in the International Herald Tribune, got the scoop from Harry Mount, author of the new book Carpe Diem: Put a Little Latin in Your Life:
"Yes, it's Priora," he told me, "because it's neuter plural. But if you cheated a bit and made the car masculine or feminine - and I do think of cars as female - then it would be Priores. And Priores has nice undertones of grandness - Virgil used it to mean 'forefathers' or 'ancestors.' "
To me, Priora seems the best, even if Prius as a car name is a new use of the word.
However, if Prius is not, in fact, a noun in Latin, but means 'to go before' or 'leading', then declining it is not really logical, is it?
And it would make sense for Toyota to use the word 'prius' as a car name to denote a leading edge.
I guess that Priuses is going to make it though since English does form plurals as it sees fit. That is, as people will say it.
Just let the two syllable exception ride.
It was my first thought on the subject.
For no other reason than it feels right to say.
So as I beg to differ, I will go for the French version of Priee.
smell the same".I am not a Language Guru.A SURGEON ,genome XX,Fiercely
Committed to the economic health and growth of America. Call THIS GENRE
OF NEW CARS AS A NEW HYBRID SPECIES --PRIUSIES
FOREVER AND A DAY
R FERNANDO MD
Consequently, when used as a noun or adjective, its plural MUST be "prii", the same a "foci" for "focus", "loci" for "locus", and so on.
Here is the usage of the three ways prius can be used:
ADJECTIVE
prior, previus, ahead, in front, leading; previous, earlier, preceding, prior; former; basic;
ADVERB
earlier, before, previously, first;
NOUN:
lesser, earlier times/events/actions; a logically prior proposition
Either adjectival or adverbial uses have possible meanings, 'going before', 'leading', or 'first'.
It must take on the plurification rules of the speaker's language. British and US English: Priuses, just like Lexuses, Marcoses, Augustuses, Lucases,and vomitouses, not to be confused with the troublesome phlegm.
The interesting question is: What do you call a group of Priuses? A pride, a gaggle, herd, a school, a pack, a band, a cohort, or praps, a battery.
[Italics omitted.]
John S Dublin
But even Priuses is easy to say...and helps connect with the masses...
Further evidence: "We know of Columbus, Ohio, but how many other Columbuses are there in the US?"
But we also must recognise there is a place in our language to create new words which more aptly describe the circumstance / use to which the word is being employed, so may be we might put aside rectitude and give some thought to a new word which would be fitting to describe more than one "Prius" shall we give it a go? and have some fun.
I got curious, so I did a search on "noun identical plural." No need for a "two syllable" exception. I found several right off the bat: bison, salmon, aircraft (and similar forms), cannon, scissors, trousers. If you want more than two syllables: headquarters, pyjamas.
Priuses for real and Prii for fun.