Prius (automobile)

2019 Toyota Prius 

The Toyota Prius is a full hybrid electric automobile developed by Toyota and manufactured by the company since 1997.

When Toyota was namining the world's first mass-produced hybrid vehicle, they wanted a name that would connect to it being groundbreaking and the predecessor of the cars of the future. They turned to latin and chose "prius," meaning "first," "original," or "to go before."  It is the root of our modern word "prior."

An odd controversy surrounding the name emerged when people wanted to refer to more than one of the cars. What is the correct plural form?

The two leading contenders were "Prii" and "Priuses." Toyota initially said the plural was "Prius" (like moose or deer). But in February 2011, Toyota USA asked the US public to decide on what the most proper plural form of Prius should be. The choices included Prien, Prii, Prium, Prius, or Priuses. "Prii" was the most popular choice, but it was close - “Prii” received 25% but “Prius” came in a close second with 24%.

Technically, in Latin, the plural of “Prius” is actually “Priora” or “Priores.” (Latin assigns gender to nouns. “Priores” is the feminine plural, while “Priora” would be the neuter plural form.) Priora is a brand name used for a Russian automobile, the Lada Priora in 2007.

And don't be surprised if you still hear people use "Priuses" as the plural in English.