And if you look at this system here, which is a circle or a sphere, it's basically the collective energy of all the different molecules found within the system. So you sum their kinetic energies and you sum their potential energies, and that gives you, this guy here, the total infernal energy of the system. What this is is it's the work done to displace environment in creating the current state of the system, okay? And what that basically means is in order to get from nothing to this volume and pressure, these molecules have to do work on the environment and displacing them in forming this structure, this sphere or the circle. So what enthalpy is, it's the total energy of the system plus the work that the system has to do on the environment in creating that system. And that's what enthalpy is.