In organic chemistry, a<unk>  is one in which a series of carbon atoms are connected together to form a loop or ring. Benzene is a well known example.
The term "polycyclic" is used when more than one ring is combined in a single molecule, and the term "macrocycle" is used for a ring containing more than a dozen atoms.
Cyclic compound
Heterocyclic compound
Polycyclic compound
Diradical
Biopolymer
Complex 
Organic compound
Metabolic intermediate