with . This is the torus
which is generally meant when the term "torus" is used without qualification.
The inversion of a ring torus is a ring cyclide if
the inversion center does not lie on the torus
and a parabolic ring cyclide if it does.
The above left figure shows a ring torus, the middle a cutaway, and the right figure
shows a cross section of the ring torus through
the -plane.
. This is the torus
which is generally meant when the term "torus" is used without qualification.
The inversion of a ring torus is a ring cyclide if
the inversion center does not lie on the torus
and a parabolic ring cyclide if it does.
The above left figure shows a ring torus, the middle a cutaway, and the right figure
shows a cross section of the ring torus through
the 
-plane.
