Event horizon: The radius which a spherical mass should be compressed to in order to convert it into a black hole, or the radius at which the time and space switch responsibilities. Once within the event horizon, it is basically impossible to escape to the outer surface. Moreover, nothing can save a particle from hitting the singularity in a very short quantity of correct time once it has entered the horizon. In this logic, the event horizon is a "point of no return."
The radius of the event horizon, r, for generalized black holes (that is in geometrized units) is
r = m + (m2 - q2 - s/m2)1/2,
Here m is the mass of the hole, q is its electric charge, and s is its angular momentum.