MASS

                           In physics, mass refers to the quantity of matter in an object. More specifically, inertial mass is a quantitative measure of an object's resistance to acceleration. In addition to this,gravitational mass is a quantitative measure that is proportional to the magnitude of the gravitational force which is

1. exerted by an object (active gravitational mass), or
2. experienced by an object (passive gravitational force)

when interacting with a second object. The SI unit of mass is the kilogram (kg).