Category:Ellipticity

El`lip*tic"i*ty, n. Etym: [Cf. F. ellipticité.]

Defn: 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

Note: Some writers use ellipticity as the ratio of the difference of the two semiaxes to the minor axis, instead of the major. Nichol.