What would be the correct plural of Prius, and why?

A Latin professor would say Prium’s the best...
  • 11
    I would say Priuses.
    – Robusto
    Jan 12, 2011 at 2:26
  • 3
    Horrible little ecno-boxen? Jan 12, 2011 at 4:46
  • In truth they are not bad little cars (and rather bigger on the inside than the outside.), but I couldn't resist. Jan 12, 2011 at 4:47
  • 8
    @Guffa - no, following that accursed pattern, the plural would be "Priii"!
    – psmears
    Jan 12, 2011 at 15:13
  • 1
    @Jay You mean the proper inflection (or inflexion), not declension. It’s not like they’re telling you whether it’s a 1st declension vs 2nd declension vs 3rd declension vs the 4th declension vs the 5th declension. And I really hate the 3rd declension; just had to get that in. :) I wish the damned Romans had stopped at just 2 declensions, but even Ancient Greek went to 3, and by the 3rd declension, we’re already sunk.
    – tchrist
    Jun 21, 2012 at 1:32

9 Answers 9


I suspect that Toyota's advertising department just made up a word they thought sounded nice. If it were Latin and a noun/adjective, the plural would be priora. Since this probably is not the case, Priuses seems to be the only choice.

  • 13
    Is that an a priori assumption?
    – Robusto
    Jan 12, 2011 at 2:53
  • 1
    @Robusto: The Latin plural? Both a priori and a posteriori. There can be no other plural according to grammar, and I have seen it a lot. Jan 12, 2011 at 2:58
  • 3
    @Cerberus: I guess I needed the smiley after all ...
    – Robusto
    Jan 12, 2011 at 3:19
  • 8
    @Jimi: Hehe, well, I am the sworn enemy of the advertising industry; in that role I will say that there was probably no more to it than some brainstorming and superficial market research by people who'd never seen a decent book! <draws sword and approaches giant windmill> Jan 12, 2011 at 3:47
  • 4
    @oosterwal: In Latin, "prius" is the neuter form of the adjective "prior"; the neuter form also happens to be used as an adverb for comparatives. If we took it as an adjective, a plural form could theoretically be used. Feb 14, 2011 at 0:23

I wish people would stop referring to the latin/greek roots and words. According to normal grammatical rules assuming the Prius is a proper noun (which it is), then you simply add an "s" but since it ends in "s" you add "es". So it is properly Priuses. I have a friend named Gus and an uncle named Gus as well. When I am with both of them I am with 2 Guses. Not Guii or Gusiay or whatever. You cannot under any circumstances change the name of something. If you have a Prii then you have no Priuses.


Octopus -> Octopi

Prius -> Prii (pronounced pree-eye).

That's my story, and I'm sticking to it. I plan on never being anywhere where more than one Prius is present. That way, I will never have to use it in conversation.

All jokes aside, I don't think proper nouns are supposed to be subject to the rules of plurality, and Priuses would be the most common usage.

EDIT: Apparently Toyota actually had a poll about this, and the "offical" answer from Toyota is now prii. It goes along with a big ad campaign about their new Prius models. I'm not sure how I feel about this.

  • 2
    Dictionaries tend not to agree on octopi. I'll give you that. Merriam-Webster indicates plural oc·to·pus·es or oc·to·pi - merriam-webster.com/dictionary/octopus The online oxford English dictionary counters with this: The standard plural in English of octopus is octopuses. However , the word octopus comes from Greek, and the Greek plural form octopodes is still occasionally used . The plural form octopi is mistakenly formed according to rules for Latin plurals, and is therefore incorrect. I'm with Webster on this one, but there is room for disagreement.
    – Zoot
    Jan 12, 2011 at 16:29
  • 1
    In all this debate we do sometimes forget that octopus is in fact a Latin word.
    – nohat
    Jan 12, 2011 at 23:24
  • As Zoot says, "octopodes" would be the actual Greek plural for "octopus". Similarly, "antipus" would be the actual Greek singular for "antipodes." The use of these forms in English is not recommended. Mar 9, 2011 at 20:01
  • Many words that come to English from Greek words ending -ος take the Latinate endings -us in the singular, and either -i or -uses (or both) in the plural. For example discus, abacus, brontosaurus, platypus, hippopotamus, sarcophagus, hippocampus. This is similar to the way the Greek diphthong αι regularly gets changed to the Latin equivalent ae (later e in AmE) (haematology/hematology) or οι to oe (or e) (oestrogen or estrogen).
    – psmears
    Jun 4, 2011 at 13:17
  • But, as others have hinted, the -us in octopus does not in fact come from Greek -ος, but rather from -ους, via another regular change ου -> u (like the first u in museum).
    – psmears
    Jun 4, 2011 at 14:04

Even if we assume that "Prius" is Latin, not all Latin words that end in -us are made plural by changing the -us to -i. As Cerberus notes, in Latin "prius" is the neuter form of the adjective meaning "before" -- with the masculine and feminine forms both being "prior". The plural of "prius" in Latin is "priora". (Cerberus said all this between his original post and later comment so I upvoted his answer, but perhaps this clarifies a little.)

But just because an English word looks like a Latin word doesn't make it a Latin word, especially when it's the name of a product, which would often be a made-up word.

I'm reminded of the story of the Latin professor who reported to the police that he had been mugged. "Could you identify the hoodlums?" the policeman asks. And the professor pedantically replies, "You mean 'hoodla'."


The plural of Prius is Prius cars or more formally, Prius automobiles.

Marketers. Sheesh.

  • 5
    Those are the plurals of "Prius car" and "Prius automobile", not the plural of Prius.
    – Kosmonaut
    Jan 13, 2011 at 1:28
  • No way :) Thanks, @Kosmonaut. @ghoppe: Well, you could say that's a great way to avoid having to pluralize Prius directly!
    – Jimi Oke
    Jan 13, 2011 at 3:00
  • @Kosmonaut The point I am making is that this question is just a repeat of marketing drivel. (Mostly) no one is really concerned that the plural of Prius is cumbersome, any more than the plural of say, Dodge is cumbersome. You would seldom hear "he owns two Dodges" (because the word is also a verb and sounds weird) you would hear "he owns two Dodge trucks". Same goes with Prius. My sister has owned two Prius cars.
    – ghoppe
    Jan 14, 2011 at 19:35
  • 2
    Hm. I agree with you that some things are simply marketing drivel, but in my experience it is quite common to call vehicles Fords, Jeeps, Saturns, and whatnot. The thing I am surprised about is that I've heard Priuses as the plural of Prius many times, and nothing else. I hadn't realized people were unsure of how to pluralize it.
    – Kosmonaut
    Jan 14, 2011 at 23:09
  • 1
    I think you have it exactly backwards. If Toyota marketing care about the question, they will probably assert that the plural is as you says, just as Sony marketing insist that the plural of Walkman is "Walkman personal stereos". The rest of us ignore the marketeers, and carry on saying Walkmans and Priuses (or Walkman and Prii if we feel like it)
    – Colin Fine
    Jun 6, 2011 at 11:05

There is no correct plural for the word Prius at the moment. The matter is still up for debate. It is left to Toyota to determine what this should be. The company has, however, graciously opted to standardize the plural of Prius based on popular opinion. To contribute or make your voice heard on what you think the correct plural form should be, go cast your vote on the Toyota website website. The options are: priuses, prium, prien, prius and prii.

  • 2
    No. Toyota can decide what they want it to be. The rest of the English-speaking world may or may not decide to follow them.
    – Colin Fine
    Jun 6, 2011 at 11:07
  • I disagree. OED's (1989) entry prius - that which takes precedence; the superior, first, chief doesn't give a plural. Presumably because they thought the plural would never be relevant to anything. Imho, Toyota's use is effectively a neologism - it's extremely rare for neologisms to be irregular, so on any rational basis the "correct" plural should Priuses. And as Colin implies, it probably wouldn't make much difference if Toyota chose to push for something different (but I can't imagine they would). Jun 20, 2012 at 23:50

Prius is a loanword from the Japanese puriusu (プリウス), an abbreviation of puritii usuita. puritii (プリティー) is, in turn, a loanword from English: pretty. usuita (薄板) means laminate or veneer.

When we pluralize loanwords in English, we can choose to either follow the pattern of the original language or simply follow the English rules. In general, Japanese lacks plural forms (or, to put it another way, every noun is a mass noun) which is why, for instance, samurai is often pluralized as just samurai.

So you can choose:

  • A greenwash (the collective noun)
  • Prius (follow the Japanese pattern)
  • Priuses (follow the English pattern)
  • Whatever dumb form Toyota's marketing department comes up with (not recommended)
  • Are options (1) and (4) distinct, then? Who came up with a greenwash of Priuses? :) Oct 30, 2012 at 22:14
  • @Quuxplusone greenwash? Well, I can't say for sure. A lot of these things are just made up, y'know.
    – Pitarou
    Oct 31, 2012 at 9:04

No plural is needed. Attributive modifiers are always used in the singular and trademarks are attributive modifiers.

Correct: Hand me the Yugoslavia report.
Correct: Hand me the Yugoslavia reports.
Incorrect: Hand me the Yugoslavias report.
Incorrect: Hand me the Yugoslavias reports.

Just as Yugoslavia identifies the country a report is attributed to, Prius identifies the named line of vehicles a car is attributed to. There is only, and can ever be, one such named line.

I suppose one could imagine a case where there were two different lines of cars both called Prius. For example, one can talk about the "Koreas" to mean both North and South Korea. But that would be the only case where one would need a plural of Prius.

Incorrect: I could have had two V8's.
Correct: I could have had two V8 brand vegetable juice beverages.
Correct: Both my wife and I have Prius cars.
Correct: My car is a Prius, and so is my wife's.
Ambiguous: I'm glad I'm a man, and so is my wife.

You can read these, and many other fine rules that no sane person follows, in INTA's trademark usage guide.

  • So it's wrong to say, "There are two Fords in the parking lot" or "I drank two Cokes yesterday"? I don't know what rule that breaks, or why we should obey such a rule.
    – Jay
    Apr 17, 2017 at 17:25
  • @Jay See my link which answers (or at least tries to answer) both of those questions. Apr 17, 2017 at 18:03

Since we're all geeks on this here intermanet-thingy, I propose we use geek-speak and declare the plural of Prius is Priussen (like the plural of VAX is VAXXEN.)

  • 3
    No, the plural of Vax - in certain circles - is Vaxen (single "x").
    – psmears
    Jun 4, 2011 at 13:00
  • We call them vaxen and boxen to match the plural of ox. By that line of reasoning, it should be prii. Yuck!
    – Pitarou
    Jun 21, 2012 at 5:25
  • Surely if we're trying to match the plural of ox, the best answer is Proxen. ;) Oct 30, 2012 at 22:15

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