ellipticity

• POS: Noun
• HYPHEN: el=lip=tic=i=ty

CIDE DICTIONARY

ellipticity, n. [Cf. F. ellipticité.].

 Deviation of an ellipse or a spheroid from the form of a circle or a sphere; especially, in reference to the figure of the earth, the difference between the equatorial and polar semidiameters, divided by the equatorial; thus, the ellipticity of the earth is 1913 Webster]
" Some writers use ellipticity as the ratio of the difference of the two semiaxes to the minor axis, instead of the major."  Nichol.  [1913 Webster]