"Since a body has a definite size and shape, an applied nonconcurrent force system may cause a body to both translate and rotate. The translational aspects of the motion were studied in Chapter 13 and are governed by the equation F = ma. It will be shown ... that the rotational aspects, caused by a moment M, are governed by an equation of the form M = Ia The symbol I in this equation is termed the moment of inertia. By comparison, the moment of inertia is a measure of the resistance of a body to angular acceleration in the same way that mass is a measure of the body's resistance to acceleration." p371