The relative difference between “polar” and “mean” values of this quantity defines the dynamical ellipticity. A 2-to-2-to-1 ratio of components of this quantity characterizes the Kovalevskaya top. In Poinsot’s (10[1])construction, an ellipsoid named for this quantity rolls without slipping on the invariable plane. A body with three distinct values of this quantity only has stable motion about (10[1])the first and third “principal” types of a certain construct. The fact that this quantity equals the integral of “r-squared dm” is used to prove that a displacement d changes this quantity by a factor of “m plus d-squared” in the parallel axis theorem. An analogue (10[1])of Newton’s second law states that net torque equals this quantity times angular acceleration. For 10 points, name this rotational analogue of mass. ■END■