ellipse -
a closed plane curve resulting from the intersection of a circular cone and a plane cutting completely through it; "the sums of the distances from the foci to any point on an ellipse is constant"
ellipse -
To remove from a phrase a word which is grammatically needed, but which is clearly understood without having to be stated.
Wikipedia
An ellipse (from Greek ἔλλειψις elleipsis, a "falling short") is a plane curve that results from the intersection of a cone by a plane in a way that produces a closed curve. Circles are special cases of ellipses, obtained when the cutting plane is perpendicular to the cone's axis. An ellipse is also the locus of all points of the plane whose distances to two fixed points add to the same constant.
OmegaWiki Dictionary
Ω
ellipse A curved planar figure, the locus of all points which have the same total distance from two fixed points called the foci.
