How do I call the back of a pick up?

I heard it's called the bed or the box? I dunno o3o

Here in Aus, what you call pick up trucks we call "utes", the back of which are called "the tray". Though in normal car it would just be a "boot".

Tempted to start a forum called "I say tomato, you say..." and have people put their own regional words or pronunciations, then have others comment and put their own equivalent. Could be interesting... Or maybe I'm just a linguistics nerd xD

The deck. I think our main NZ brand is Tuff Deck.