Moment of inertia, also called "angular mass", is the inertia of a rotating body with respect to its rotation. It is a rotating body's resistance to angular acceleration or deceleration, equal to the product of the mass and the square of its perpendicular distance from the axis of rotation.

moment of inertia (plural moments of inertia) ( physics , classical mechanics ) A measure of a rigid body's resistance to change in its angular velocity around a given axis. The moment of inertia of a rigid body is a quantity that determines the torque needed for a desired angular acceleration about a given rotational axis, in close analogy to the way mass determines the force needed for …

Moment of inertia is defined as the product of mass of section and the square of the distance between the reference axis and the centroid of the section. Spinning figure skaters can reduce their moment of inertia by pulling in their arms, allowing them to spin faster due to conservation of angular momentum.

If instead of force, the area of the figure or mass of the body is considered, it is called the second moment of area or second moment of mass. They are also termed broadly as moments of inerta. There is no physical significance for moment of inertia. It is just a mathematical expression usually denoted by

The moment of inertia is a physical quantity which describes how easily a body can be rotated about a given axis. It is a rotational analogue of mass, which describes an object's resistance to translational motion.