Dictionary.com
Thesaurus.com

radius of curvature

American  

noun

Mathematics.
  1. the absolute value of the reciprocal of the curvature at a point on a curve.


radius of curvature British  

noun

  1. the absolute value of the reciprocal of the curvature of a curve at a given point; the radius of a circle the curvature of which is equal to that of the given curve at that point See also centre of curvature

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Etymology

Origin of radius of curvature

First recorded in 1745–55