A three dimensional solid formed by revolving, not rotating a disc about a line. In the Cartesian Plane, if the disc is revolved about the y-axis, its shape (the cross-section of the toroid) is given by the equation (x-b)2 + y2 = a2. (i.e. a circle, with radius a, centered at the point (b,0)) The volume of this toroid is then given by V = 2Pi2a2b.