ellipsoid

== English == === Etymology === From ellipse +‎ -oid. === Pronunciation === (UK) IPA(key): /ɪˈlɪp.sɔɪd/ (US) IPA(key): /ɪˈlɪp.sɔɪd/, /əˈlɪp.sɔɪd/, /iˈlɪp.sɔɪd/ (General Australian) IPA(key): /əˈlɪp.soɪd/, /ɪˈlɪp.soɪd/ === Noun === ellipsoid (plural ellipsoids) (mathematics, geometry) 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. (geography) Such a surface used as a model of the shape of the earth. ==== Usage notes ==== The general case, with semiaxes a, b and c all different, is a triaxial ellipsoid (more rarely, scalene ellipsoid). If two are the same, say b = c, the result is an ellipsoid of revolution, which may be oblate (if a < b) or prolate (a > b). The degenerate case a = b = c is a sphere. An ellipsoid of revolution is also called a spheroid. ==== Hypernyms ==== quadric surface, quadric ==== Derived terms ==== ==== Related terms ==== ellipsoidal subellipsoid ==== Translations ==== ==== See also ==== geoid === Adjective === ellipsoid (comparative more ellipsoid, superlative most ellipsoid) Shaped like an ellipse; elliptical. (mathematics) Of or pertaining to an ellipse; elliptic. (botany) Having the tridimensional shape of an ellipse rotated on its long axis. ==== Related terms ==== ellipsoidal globoid ovoid ==== Translations ==== === See also === globose oblong == Swedish == === Noun === ellipsoid c (mathematics) ellipsoid ==== Declension ====