Inertia

Inertia (Lat., 'inactivity'), a universal property of matter, fully described in Newton's first law of motion, which asserts that every body perseveres in its state of rest or of uniform motion in a straight line except in so far as it is compelled by force to alter that state. Part of this principle was known to the ancients, and by them attributed to a certain repugnance to motion, which was a characteristic of all matter; but it was shown by Galileo that just as the body at rest could not of itself begin to move, so the body in motion could not of itself come to rest.—The Moment of Inertia is the sum of the products of every particle of a mass into the corresponding distance from a given point or axis of rotation.