Illustrated Glossary of Organic Chemistry

Polycyclic: A molecule having more than one ring. Usually applied to molecules have four or more rings.

Bicyclic molecules such as naphthalene and nepetalactone have two rings.


Tricyclic molecules such as phenanthrene (shown here) have three rings.

Cholesterol		Benzo[a]pyrene		Graphite

Cholesterol (four rings), benzo[a]pyrene (five rings) and graphite (millions of rings) are all polycyclic structures.