Oh. Hm. It is the first time he's had to explain the term, though it does seem like Eren at least knows what a bear is - or so Billy hopes, anyway. Maybe there wouldn't be animals like that in a world filled with monsters?

"It is a region very far up north where I come from," he explains, trying to keep it as basic as possible. It feels strange to explain it in terms that usually would be reserved for small children, but despite having been here for a while now, Billy is still getting used to the cultural clashes.

Still, he sounds polite about it as he speaks.

"It is very cold there. It mostly consists of ice-- so not many creatures or people can live there. There are bears there though that have adapted to the climate, those are called polar bears." It would have been an easier explanation of Eren knew what those were, but if he doesn't know about the Arctic, then of course he wouldn't know about those either. Where else would those animals have to live? "The one we met was not a regular bear at all. It seemed.. intelligent."

Billy frowns a little as he says it. It still feels ridiculous, like he's talking about something impossible, but he can no longer deny this just is what was going on in his world.

"It was hunting us down the way a human might, not the way a beast might, if that makes any sense at all."