Toyota have announced the results of a competition they ran to decide what the plural form for the Toyota Prius should be. Prii wasnt the only contender though, there were a few other terms that nearly won.
Toyota ran a 6 month campaign, during which 1.8 million votes were cast. The other options that could be voted for were Prius (like the plural of fish), Priuses, Prium and Prien.
Prii won with 25% of the votes, just beating Prius which got 24% of the votes.
Were very glad that neither Prium or Prien won, it would have sounded ever so slightly pretentious!