The moment of inertia ($I$) represents a body's resistance to rotational acceleration, analogous to mass in linear motion. $I=\sum m_i{r}_i^2$ where $r_i$ is the perpendicular distance of mass element $m_i$ from the axis of rotation.

• It depends on the total mass.
• It depends heavily on the distribution of mass (how far it is from the axis).
• It depends on the choice of axis (the same object has different $I$ for different axes).