What is "angle of curvature"

Curvature \Cur"va*ture\ (k?r"v?-t?r; 135), n. [L. curvatura. See Curvate.]

1. 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.
   --Cowper.

   The elegant curvature of their fronds.
   --Darwin.

2. (Math.) 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.

   Aberrancy of curvature (Geom.), the deviation of a curve from a circular form.

   Absolute curvature. See under Absolute.

   Angle of curvature (Geom.), one that expresses the amount of curvature of a curve.

   Chord of curvature. See under Chord.

   Circle of curvature. See Osculating circle of a curve, under Circle.

   Curvature of the spine (Med.), an abnormal curving of the spine, especially in a lateral direction.

   Radius of curvature, the radius of the circle of curvature, or osculatory circle, at any point of a curve.