Affine curvature

This article is about the curvature of affine plane curves, not to be confused with the curvature of an affine connection.

Special affine curvature, also known as the equi-affine curvature or affine curvature, is a particular type of curvature that is defined on a plane curve that remains unchanged under a special affine transformation (an affine transformation that preserves area). The curves of constant equi-affine curvature k are precisely all non-singular plane conics. Those with k > 0 are ellipses, those with k = 0 are parabolas, and those with k < 0 are hyperbolas.