Cassini oval

Etymology
Named after the astronomer, who studied them in 1680.

Noun

 * 1)  A plane curve defined as the set (or locus) of points in the plane such that the product of the distances to two fixed points is constant (related to an ellipse, for which the sum of the distances is constant).

Synonyms

 * Cassini ellipse
 * cassinoid
 * oval of Cassini

Translations

 * French: