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An explicit distinction between 'thermal equilibrium' and 'thermodynamic equilibrium' is made by B. C. Eu. He considers two systems in thermal contact, one a thermometer, the other a system in which there are occurring several irreversible processes, entailing non-zero fluxes; the two systems are separated by a wall permeable only to heat. He considers the case in which, over the time scale of interest, it happens that both the thermometer reading and the irreversible processes are steady. Then there is thermal equilibrium without thermodynamic equilibrium. Eu proposes consequently that the zeroth law of thermodynamics can be considered to apply even when thermodynamic equilibrium is not present; also he proposes that if changes are occurring so fast that a steady temperature cannot be defined, then "it is no longer possible to describe the process by means of a thermodynamic formalism. In other words, thermodynamics has no meaning for such a process."<ref>Eu, B.C. (2002), page 13.</ref> This illustrates the importance for thermodynamics of the concept of temperature.

An explicit distinction between 'thermal equilibrium' and 'thermodynamic equilibrium' is made by B. C. Eu. He considers two systems in thermal contact, one a thermometer, the other a system in which there are occurring several irreversible processes, entailing non-zero fluxes; the two systems are separated by a wall permeable only to heat. He considers the case in which, over the time scale of interest, it happens that both the thermometer reading and the irreversible processes are steady. Then there is thermal equilibrium without thermodynamic equilibrium. Eu proposes consequently that the zeroth law of thermodynamics can be considered to apply even when thermodynamic equilibrium is not present; also he proposes that if changes are occurring so fast that a steady temperature cannot be defined, then "it is no longer possible to describe the process by means of a thermodynamic formalism. In other words, thermodynamics has no meaning for such a process."<ref>Eu, B.C. (2002), page 13.</ref> This illustrates the importance for thermodynamics of the concept of temperature.

热平衡和热力学平衡之间的明确区分是由 B.C. Eu 提出的。他认为两个系统在热接触，一个是温度计，另一个是一个系统，其中有几个不可逆过程，产生非零通量; 这两个系统被一个只透热的壁隔开。他考虑了这样一种情况，在有兴趣的时间尺度上，温度计读数和不可逆过程都是稳定的。然后是没有热平衡的热力学平衡。因此，欧盟提出，即使在没有热力学第零定律的情况下，也可以考虑应用热力学平衡; 他还提出，如果变化发生得太快，以至于无法确定一个稳定的温度，那么“用热力学形式主义来描述这一过程就不再可能了。换句话说，热力学对这样一个过程没有意义。“这说明了温度概念对热力学的重要性。

热平衡和热力学平衡之间的明确区分是由 B.C.Eu 提出的。他认为两个系统在热接触，一个是温度计，另一个是一个系统，其中有几个不可逆过程，产生非零通量; 这两个系统被一个只透热的壁隔开。他考虑了这样一种情况，在有兴趣的时间尺度上，温度计读数和不可逆过程都是稳定的。然后是没有热平衡的热力学平衡。因此，Eu提出，即使在没有热力学第零定律的情况下，也可以考虑应用热力学平衡; 他还提出，如果变化发生得太快，以至于无法确定一个稳定的温度，那么“用热力学形式主义来描述这一过程就不再可能了。换句话说，热力学对这样一个过程没有意义。”这说明了温度概念对热力学的重要性。

A system's internal state of thermodynamic equilibrium should be distinguished from a "stationary state" in which thermodynamic parameters are unchanging in time but the system is not isolated, so that there are, into and out of the system, non-zero macroscopic fluxes which are constant in time.

A system's internal state of thermodynamic equilibrium should be distinguished from a "stationary state" in which thermodynamic parameters are unchanging in time but the system is not isolated, so that there are, into and out of the system, non-zero macroscopic fluxes which are constant in time.

Non-equilibrium thermodynamics is a branch of thermodynamics that deals with systems that are not in thermodynamic equilibrium. Most systems found in nature are not in thermodynamic equilibrium because they are changing or can be triggered to change over time, and are continuously and discontinuously subject to flux of matter and energy to and from other systems. The thermodynamic study of non-equilibrium systems requires more general concepts than are dealt with by equilibrium thermodynamics. Many natural systems still today remain beyond the scope of currently known macroscopic thermodynamic methods.

Non-equilibrium thermodynamics is a branch of thermodynamics that deals with systems that are not in thermodynamic equilibrium. Most systems found in nature are not in thermodynamic equilibrium because they are changing or can be triggered to change over time, and are continuously and discontinuously subject to flux of matter and energy to and from other systems. The thermodynamic study of non-equilibrium systems requires more general concepts than are dealt with by equilibrium thermodynamics. Many natural systems still today remain beyond the scope of currently known macroscopic thermodynamic methods.

Thermal equilibrium occurs when a system's [[macroscopic]] thermal observables have ceased to change with time.  For example, an [[ideal gas]] whose [[Distribution function (physics)|distribution function]] has stabilised to a specific [[Maxwell–Boltzmann distribution]] would be in thermal equilibrium.  This outcome allows a single [[temperature]] and [[pressure]] to be attributed to the whole system. For an isolated body, it is quite possible for mechanical equilibrium to be reached before thermal equilibrium is reached, but eventually, all aspects of equilibrium, including thermal equilibrium, are necessary for thermodynamic equilibrium.<ref>de Groot, S.R., Mazur, P. (1962), p. 44.</ref>

Thermal equilibrium occurs when a system's [[macroscopic]] thermal observables have ceased to change with time.  For example, an [[ideal gas]] whose [[Distribution function (physics)|distribution function]] has stabilised to a specific [[Maxwell–Boltzmann distribution]] would be in thermal equilibrium.  This outcome allows a single [[temperature]] and [[pressure]] to be attributed to the whole system. For an isolated body, it is quite possible for mechanical equilibrium to be reached before thermal equilibrium is reached, but eventually, all aspects of equilibrium, including thermal equilibrium, are necessary for thermodynamic equilibrium.<ref>de Groot, S.R., Mazur, P. (1962), p. 44.</ref>

当一个系统的'''<font color="#ff8000">宏观 Macroscopic</font>'''热观测量不再随时间变化时，就会出现热平衡。例如，一种'''<font color="#ff8000">分布函数 Distribution Function</font>'''稳定到一个特定的'''<font color="#ff8000">麦克斯韦-波兹曼分布 Maxwell–Boltzmann distribution</font>'''的'''<font color="#ff8000">理想气体 Ideal Gas</font>'''将在热平衡。这个结果可以将单一的'''<font color="#ff8000">温度 Temperature</font>'''和'''<font color="#ff8000">压力 Pressure</font>'''归因于整个系统。对于一个孤立的物体来说，在达到力学平衡之前达到热平衡是很有可能的，但是最终，所有方面的平衡，包括热平衡，对于热力学平衡来说都是必要的。

当一个系统的'''<font color="#ff8000">宏观 Macroscopic</font>'''热观测值不再随时间变化时，就会出现热平衡。例如，一种'''<font color="#ff8000">分布函数 Distribution Function</font>'''稳定到一个特定的'''<font color="#ff8000">麦克斯韦-波兹曼分布 Maxwell–Boltzmann distribution</font>'''的'''<font color="#ff8000">理想气体 Ideal Gas</font>'''即处于热平衡状态。这个结果可以将单一的'''<font color="#ff8000">温度 Temperature</font>'''和'''<font color="#ff8000">压力 Pressure</font>'''归因于整个系统。对于一个孤立的物体来说，在达到热平衡之前达到机械平衡是可能的，但是最终，所有方面的平衡，包括热平衡，对于热力学平衡来说都是必要的。

Laws governing systems which are far from equilibrium are also debatable. One of the guiding principles for these systems is the maximum entropy production principle.  It states that a non-equilibrium system evolves such as to maximize its entropy production.

Laws governing systems which are far from equilibrium are also debatable. One of the guiding principles for these systems is the maximum entropy production principle.  It states that a non-equilibrium system evolves such as to maximize its entropy production.