The maximum and minimum of the normal curvature κ_1 and κ_2 at a given point on a surface are called the principal curvatures. The principal curvatures measure the maximum and minimum bending of a regular surface at each point. The Gaussian curvature K and mean curvature H are related to κ_1 and κ_2 by K | = | κ_1 κ_2 H | = | 1/2(κ_1 + κ_2).