the quality of being rash and foolish; "trying to drive through a blizzard is the height of folly"; "adjusting to an insane society is total foolishness"
a circularity that has a different center or deviates from a circular path
(geometry) a ratio describing the shape of a conic section; the ratio of the distance between the foci to the length of the major axis; "a circle is an ellipse with zero eccentricity"