[ Idioms are hard, but his explanation helps immensely. So Eleven nods, even though Bucky can't see it. ]

A rain check is a promise. To do something later.

[ She parrots him - and just like that, she adds it to her list of truths about the world. Congratulations Bucky - you have influence over this child. ]

Friends are important. [ Sage wisdom. ] I understand. If you want. I'll protect your friends, too.