curvature vs incurvature

curvature

noun

  • The shape of something curved. 

  • The extent to which a Riemannian manifold is intrinsically curved. 

  • The extent to which a subspace is curved within a metric space. 

incurvature

noun

  • curvature; curving 

How often have the words curvature and incurvature occurred in a corpus of books? (source: Google Ngram Viewer )