Curvature is a value equal to the reciprocal of the radius of the circle or sphere that best approximates the curve at a given point. This can be computed for functions and parameterized curves in various coordinate systems and dimensions. Related properties, such as the radius of curvature and center of curvature, are also easily computed by Wolfram|Alpha.
Compute curvature for functions and curves in various coordinate systems.
Compute the curvature of a plane curve at a point: