When a thermodynamic system is considered on the microscopic scale, equilibrium is associated with the distribution of molecules that has the greatest probability of occurring, i.e. the state with the greatest degree of disorder. Statistical mechanics interprets the increase in entropy in a closed system to a maximum at equilibrium as the consequence of the trend from a less probable to a more probable state. Any process in which there is no change in entropy occurs is said to be isentropic.
Entropy also appears in statistical mechanics as a function of the number of possible microscopic states (W) that a system of atoms or molecules could occupy, consistent with its macroscopic state (temperature, presure etc).
Also Known As: S, disorder