Moment of inertia

Scalar measure of the rotational inertia with respect to a fixed axis of rotation

The moment of inertia (also known as mass moment of inertia, angular/rotational mass, second moment of mass, or rotational inertia) is a measure of how difficult it is to change the rotation rate of a rigid body about a given axis. It is the ratio between the torque applied and the resulting angular acceleration about that axis. It plays the same role in rotational motion as mass does in linear motion.

From Wikipedia, under CC BY-SA. More on occurri.