In
chemistry, a
ring is an ambiguous term referring either to a
simple cycle of atoms and bonds in a molecule or to a connected set of atoms and bonds in which every atom and bond is a member of a cycle (also called a
ring system). A ring system that is a simple cycle is called a
monocycle or
simple ring, and one that is not a simple cycle is called a
polycycle or
polycyclic ring system. A simple ring contains the same number of
sigma bonds as atoms, and a polycyclic ring system contains more sigma bonds than atoms.