In geometry, a spherical segment is the solid defined by cutting a sphere or a ball with a pair of parallel planes. It can be thought of as a spherical cap with the top truncated, and so it corresponds to a spherical frustum.
The surface of the spherical segment (excluding the bases) is called spherical zone.
If the radius of the sphere is called , the radii of the spherical segment bases are and and the height of the segment (the distance from one parallel plane to the other) called , then the volume of the spherical segment is
The curved surface area of the spherical zone—which excludes the top and bottom bases—is given by