Equipartition usually refers to the fact that
in classical statistical mechanics each degree of freedom that appears quadratically in the energy (Hamiltonian) has an average value of , where is the thermal energy.
Thus, the thermal energy is shared equally ("equipartitioned") by all these degrees of freedom. This is a consequence of the equipartition theorem, which is very simple mathematically. As an immediate corollary, the translational energy of a molecule must equal , since translations are described by three degrees of freedom.