Inertia - The property of matter by which it retains its state of rest or its velocity along a straight line so long as it is not acted upon by an external force.1.9: Mass and Weight
Mass - The quantity of matter as determined from its weight or from Newton's second law of motion.
Weight - The force that gravitation exerts upon a body, equal to the mass of the body times the local acceleration of gravity: commonly taken, in a region of constant gravitational acceleration, as a measure of mass.
