eccentricity
n//ˌɛk.sɛnˈtɹɪs.ɪ.ti//excentricitet
The quality of being eccentric or odd; any eccentric behaviour.
(geometry) The ratio, constant for any particular conic section, of the distance of a point from the focus to its distance from the directrix.
(astronomy) The eccentricity of the conic section (usually an ellipse) defined by the orbit of a given object around a reference object (such as that of a planet around the sun).