ellipsoid vs spherical

ellipsoid

adj
  • Shaped like an ellipse; elliptical. 

  • Having the tridimensional shape of an ellipse rotated on its long axis. 

  • Of or pertaining to an ellipse; elliptic. 

noun
  • A surface, all of whose cross sections are elliptic or circular (including the sphere), that generalises the ellipse and in Cartesian coordinates (x, y, z) is a quadric with equation x²/a² + y²/b² + z²/c² = 1. 

  • Such a surface used as a model of the shape of the earth. 

spherical

adj
  • Shaped like a sphere. 

  • Of or relating to the heavenly orbs, or to the sphere or spheres in which, according to ancient astronomy and astrology, they were set. 

  • Of a coordinate system, specifying the location of a point in a plane by using a radius and two angles. 

  • Of, or pertaining to, spheres. 

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