Prius Is a Latin word meaning "before". According to Toyota the name was chosen because the Prius was launched before environmental awareness became a mainstream social issue. In February 2011, Toyota asked the public to decide on what the most proper plural form of Prius should be, with choices including Prien, Prii, Prium, Prius, or Priuses. The company says "it will use the most popular choice in its advertising and on February 20 announced that "Prii" was the most popular choice, and the new official plural designation. In Latin prius is the neuter singular of the comparative form (prior, prior, prius) of an adjective with only comparative and superlative (the superlative being primus, prima, primum), consequently, like all 3rd declension words, the plural in Latin was priora (cf. Latin declension). There is no reason to believe , however, that any majority of English speakers (or even Prius owners) use anything but the regular English plural, Priuses.
Toyota Prius Blueprint
Toyota Prius First Generation
Production : 1997-2003
Toyota Prius Second Generation
Production : 2003-2009
Toyota Prius Third Generation
Production : 2009-
Toyota Prius Blueprint
Toyota Prius First Generation
Production : 1997-2003
Toyota Prius Second Generation
Production : 2003-2009
Toyota Prius Third Generation
Production : 2009-