Does "equilibrium" imply max. entropy in statistical mechanics? I've gotten myself confused thinking about the meaning of "equilibrium" in statistical mechanics. I thought I remembered that an isolated system at equilibrium is equally likely to be in any possible microstate, which means there would be some very tiny probability it would be in a low-entropy state far from the maximum entropy possible for the system. But when physicists talk about "non-equilibrium thermodynamics", aren't they talking about systems which are far from maximum entropy? Perhaps the difference is that non-equilibrium thermodynamics is dealing with systems that are not isolated, but are receiving energy from the outside or something? Or maybe my definition of equilibrium is wrong, and an isolated system at equilibrium is not equally likely to be in every possible microstates, but just those microstates corresponding to a maximum-entropy macrostate?