Mom: Now be careful, don't squeeze.
Colin drinks his juice carefully. Then, a few minutes later:
Colin: Mom, I know why if you squeeze a juice box or a jammer, the juice comes out. It's because when you squeeze, you take away the place where the juice was, and it has nowhere to go but to come up the straw and then spill out.
Mom: Yep, it's called "displacement".
Mom: Yes - it means you are taking away the place where the juice was.
(I love seeing kids process stuff like that on their own!)