In

geometry, the curvature of a

surface at a

point is the value of the second

derivative of the

function describing the surface, at that point. Or, more comprehensibly, if a curve is

described by f(x) (for all x), the curvature at (n, f(n)) is f''(n). This applies to

shapes which aren't just

curves, and to

curves that aren't just defined a two-dimensioanl space.

Practical examples: The curvature of a straight line is 0, the curvature of a circle is a constant.

Compare with radius of curvature.