An object which has undergone ultimate gravitational collapse. The force of gravity [gravitational forces] becomes so strong that, according to general relativity, matter and radiation which come too close to the black hole cannot be prevented by any known physical force from collapsing to a physical singularity at its centre. Matter and radiation cannot escape to the outside world from within the Schwarzschild radius of a non-rotating black hole. Black holes can possess only three properties, mass, electric charge and angular momentum