For example, I would hear people say in the "regime" of x>3? Does it have a different meaning/origin to the "region" of x>3? To me, "region" sounds like the more proper term.
Edit: I have heard this usage in a few context in physics, electrical engineering, and machine learning. It usually involves the professors pointing at a 2D graph and articulating about the behavior of a system/model/function in these "regimes".