[1] : The Collaborative International Dictionary of English v.0.48

radius \ra"dius\ r=a"di^u^s, n.; pl. l. radii
   r=a"di^imac; e. radiuses
   r=a"di^u^se^z. l., a staff, rod, spoke of a
   wheel, radius, ray. see ray a divergent line.
   1. geom. a right line drawn or extending from the center of
      a circle to the periphery; the semidiameter of a circle or
      sphere.
      1913 webster

   2. anat. the preaxial bone of the forearm, or brachium,
      corresponding to the tibia of the hind limb. see illust.
      of artiodactyla.
      1913 webster

   note: the radius is on the same side of the limb as the
         thumb, or pollex, and in man it is so articulated that
         its lower end is capable of partial rotation about the
         ulna.
         1913 webster

   3. bot. a ray, or outer floret, of the capitulum of such
      plants as the sunflower and the daisy. see ray, 2.
      1913 webster

   4. pl. zool.
      a the barbs of a perfect feather.
      b radiating organs, or color-markings, of the radiates.
          1913 webster

   5. the movable limb of a sextant or other angular instrument.
      --knight.
      1913 webster

   radius bar mach., a bar pivoted at one end, about which
      it swings, and having its other end attached to a piece
      which it causes to move in a circular arc.

   radius of curvature. see under curvature.
      1913 webster
see also:
radii radiuses ray artiodactyla radius bar radius of curvature 
curvature 

[2] : The Collaborative International Dictionary of English v.0.48

curvature \cur"vature\ 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.
      1913 webster

            the elegant curvature of their fronds. --darwin.
      1913 webster

   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.
      1913 webster

   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.
      1913 webster
see also:
curvate aberrancy of curvature absolute curvature absolute angle of curvature chord of curvature 
chord circle of curvature osculating circle of a curve circle curvature of the spine 
radius of curvature 

[3] : WordNet (r) 2.0

radius of curvature
     n : the radius of the circle of curvature; the absolute value of
         the reciprocal of the curvature of a curve at a given
         point

Radius >> R Words
Radius, definition of term: Radius
radius_pag1.html

Curvature >> C Words
Curvature, definition of term: Curvature
curvature_pag1.html