A physical system refers to any specific object, device, or arrangement of objects that can be physically observed or interacted with. It is a tangible entity that operates or functions based on the physical laws of nature. Full definition
The team is now working on computer simulations that, based on this mathematical model, can predict the behavior of physical systems. (sciencedaily.com)
This is where it really gets tricky: What's the role of prayer in physical systems? (christianitytoday.com)
However this also applies to more simple physical systems like the protein.. (realclimate.org)