Reference:Sphere

The syntax of the sphere object is:

SPHERE:
  sphere {
    <Center>, Radius
    [OBJECT_MODIFIERS...] 
    }

The geometry of a sphere.

Where <Center> is a vector specifying the x, y, z coordinates of the center of the sphere and Radius is a float value specifying the radius. Spheres may be scaled unevenly giving an ellipsoid shape.

Because spheres are highly optimized they make good bounding shapes (if manual bounding seems to be necessary).