system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 What is potential energy? Is it a philosophical thing, or does something actually change within a the subject's atoms?
gpt
Potential energy is a property of systems rather than of individual atoms.  For example, if you have two atoms which are gravitationally attracted to one another and are far apart, or two atoms which are electrically repelled by one another and are close together, or two atoms which are not chemically bonded but could be, there is energy stored in that system configuration, and we can extract that energy.

So it's at least as real as other emergent, macro-scale properties such as "temperature" and "pressure".

Whether it's as real as fundamental, micro-scale properties such as "mass" and "spin" is less clear.  It could be, if *spacetime* turns out to be emergent, but our theories of quantum gravity aren't really working well enough yet for us to say for sure.