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 Ω Ω , it is related to the configuration entropy of an isolated system via Boltzmann's entropy formula S = k B log ⁡ ⁡ Ω Ω , where S is the entropy and k B is the Boltzmann constant.