Imaginary point where the total weight of a material body may be thought to be concentrated.
Since weight and mass are proportional, the same point may also be called the centre of mass, but the centre of mass does not require a gravitational field. A body's centre of gravity may coincide with its geometric centre, especially if the body is symmetric and composed of homogeneous material. In asymmetric, unhomogeneous, or hollow objects, the centre of gravity may be at some distance from the geometric centre or even at a point in space external to the object, such as between the legs of a chair.