Multiplicity (statistical mechanics)

In statistical mechanics, multiplicity (also called statistical weight) refers to the number of microstates corresponding to a particular macrostate of a thermodynamic system. Commonly denoted ${\displaystyle \Omega }$, it is related to the configuration entropy of an isolated system via Boltzmann's entropy formula

where ${\displaystyle S}$ is the entropy and ${\displaystyle k_{\text{B}}=1.38\cdot 10^{-23}\,\mathrm {J/K} }$ is Boltzmann's constant.