In
statistical mechanics, a
microstate is a specific microscopic configuration of a
thermodynamic system that the system may occupy with a certain probability in the course of its
thermal fluctuations. In contrast, the
macrostate of a system refers to its macroscopic properties, such as its
temperature,
pressure,
volume and
density. Treatments on
statistical mechanics, define a macrostate as follows. A particular set of values of energy, number of particles and volume of an isolated thermodynamic system is said to specify a particular macrostate of it. In this description, microstates appear as different possible ways the system can achieve a particular macrostate.