The Thermodynamic equilibrium reference article from the English Wikipedia on 24-Jul-2004
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Thermodynamic equilibrium

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In thermodynamics, a thermodynamic system is in thermodynamic equilibrium if its energy distribution equals a Maxwell-Boltzmann-distribution. This allows to attribute a temperature to the system. The process that leads to a thermodynamic equilibrium is called thermalization.

A prominent example of a thermalizing system is that of a system of interacting particles that is left undisturbed.