From Greek elleipsis 'falling short,' named by Apollonius because the cutting plane's angle falls short of the cone's side.
A regular oval shape, the closed curve formed by cutting a cone with a plane that does not intersect the base.
From Greek elleipsis 'a falling short, deficit,' from elleipein 'to fall short, leave out,' from en- 'in' + leipein 'to leave.' Apollonius of Perga named it in the 3rd century BCE because the plane's angle 'falls short' of being parallel to the cone's side (which would produce a parabola). Key roots: *leykʷ- (Proto-Indo-European: "to leave, remain").