Equipartition

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 ${\frac {1}{2}}k_{B}T$,
where $k_{B}T$ 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 ${\frac {3}{2}}k_{B}T$, since translations are described by three degrees of freedom.