A condition of a surface where:
(a) For a feature other than a sphere, all points of the surface intersected by any plane perpendicular to an axis are equidistant from that axis.
(b) For a sphere all points of the surface intersected by any plane passing through a common center are equidistant from that center1.
Also called Circularity
 Source: The American Society of Mechanical Engineers. 1994. ASME Y14.5M-1994 Dimensioning and Tolerancing. New York, New York.