The people have spoken, and Toyota will obey: When it refers to more than one Prius, the term will be “Prii.”
Toyota’s monthlong online poll, seeking public opinion on the preferred plural term for its hybrid model, generated 1.8 million votes. “Prii” topped the charts with 25 percent, followed by “Prius” — double duty for both singular and plural — at 24 percent. Also-rans included “Priuses,” “Prien” and “Prium.”
But the Associated Press Stylebook, the bible for publications like this one (except when we choose to ignore it) says otherwise: Proper nouns that end in “s” get “es” at the end. So it’s “Priuses,” not “Prii.”
Granted, the poll reflects that there’s a quasi-Latin thing going on with Prius — the suggestion that the car and its hybrid powertrain are leading the way toward a new paradigm. So exceptions will be made for vehicles sold in ancient Rome. But in the United States, says the AP, there are no Prii. No Ford Foci either.