Definition:Curvature

Definition
Let $C$ be a curve defined by a real function which is twice differentiable.

The curvature of a $C$ is the reciprocal of the radius of the osculating circle to $C$ and is often denoted $\kappa$ (Greek kappa).

Also see

 * Equivalence of Definitions of Curvature


 * Definition:Radius of Curvature