Multiplicity (statistical mechanics)

In statistical mechanics, "multiplicity" refers to the number of ways a particular state or configuration can be achieved for a system of particles. It is a measure of the number of microstates corresponding to a specific macrostate. A microstate is a specific detailed configuration of a system (e.g., the positions and velocities of all particles), while a macrostate is defined by macroscopic properties such as temperature, pressure, and volume.