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.
english.stackexchange.com/users/3036/Cerberus_Reinstate_Monica
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.
english.stackexchange.com/users/8565/bigK
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.
english.stackexchange.com/users/3328/Zoot
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'."
english.stackexchange.com/users/13140/Jay
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)
english.stackexchange.com/users/16205/Pitarou
The plural of Prius is Prius cars or more formally, Prius automobiles .
Marketers.
Sheesh.
english.stackexchange.com/users/1871/ghoppe
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 .
english.stackexchange.com/users/2705/Jimi Oke
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 .
english.stackexchange.com/users/11928/David Schwartz
What would be the correct plural of  Prius , and why?  A Latin professor would say Prium’s the best...
What is the plural of Prius?
english.stackexchange.com
<grammatical-number><latin><business-language>
english.stackexchange.com/questions/8554
english.stackexchange.com/users/2210/bobobobo
It is debatable that there is no correct plural for the word "Prius" and some people would argue that no plural is needed. Strictly speaking, in Latin, the plural would be "priora". However, just because an English word looks like a Laton word doesn't make it a Latin word. Assuming that Prius is a proper noun, the convention would be to add -es, making "Priuses".  There is no final opinion as to the plural of Prius. Some have suggested "Priuses" following English grammar rules, others have suggested "priora" following Latin rules for the Latin word Prius. However, the word is of Japanese  origin meaning laminate and veneer. When Japanese pluralises words they can choose the word format in the foreign word or in Japanese. It has been decided to give the final say to the public who can vote on their favourite word from a given list on the Toyota website.
It is debatable that there is no correct plural for the word "Prius" and some people would argue that no plural is needed. Strictly speaking, in Latin, the plural would be "priora". However, just because an English word looks like a Laton word doesn't make it a Latin word. Assuming that Prius is a proper noun, the convention would be to add -es, making "Priuses".  "Priuses" is the most widely accepted term, although "Prius cars" could be used.
"Priuses" is considered to be the most common usage, although it has been said that it should be up to Toyota. The options are:  Priuses,  prium ,  prien ,  prius  and  prii . Some people would argue that there is no official plural for "Prius" and that it is for Toyota to decide what it should be. However, according to normal grammar rules, the correct answer should be "Priuses". Other alternatives include "Prii" or simply "Prius cars".
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. There is no correct plural for the word Prius at the moment.
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. There is no correct plural for the word Prius at the moment.
Toyota chose it as a good marketing name. The Latin plural s "priora" It may not be a Latin word It is a Japanese word. There is no correct plural. Toyota will decide. There are word But it is open to popular vote and there is a choice of words. No plural needed.  As it is an attibutive modifier for a trademark, no plural required.
Priuses. The plural of "Prius" in Latin is "priora". The plural of  Prius  is  Prius cars.
According to normal grammar rules, the correct plural should be "Priuses". Some would argue that there is no official plural for the word "Prius". Some believe that this is for Toyota to determine. No plural is required. Some options may include "Priuses", "Prii" or simply "Prius cars".