inversive geometry

Noun

 * 1)  The branch of geometry concerned with inversion transformations, specifically circle inversions in the Euclidean plane, but also as generalised in non-Euclidean and higher-dimensional spaces.
 * 2) * 1983,, On the Geometry of the Kepler Problem, ', Volume 90, reprinted in 1994', John Milnor, Collected Papers'', I: Geometry, page 261,
 * In particular, the non-Euclidean geometry of Lobachevsky and Bolyai, and the inversive geometry of Steiner play an important role.