Curvature

The act of curving, or the state of being bent or curved; a curving or bending, normal or abnormal, as of a line or surface from a rectilinear direction; a bend; a curve.

The amount of degree of bending of a mathematical curve, or the tendency at any point to depart from a tangent drawn to the curve at that point.

The amount by which a curve deviates from being a straight line

(medicine) a curving or bending; often abnormal; "curvature of the spine"

the rate of change (at a point) of the angle between a curve and a tangent to the curve