In chemistry, a cyclic compound is a compound in which a series of atoms is connected to form a loop or ring. While the vast majority of cyclic compounds are organic, a few inorganic substances form cyclic compounds as well, including sulfur, silanes, phosphanes, phosphoric acid, and triboric acid. Cyclic compounds may or may not be aromatic. Benzene is aromatic while cyclohexane is not. The term "polycyclic" is used when more than one ring is formed in a single molecule for instance in naphthalene, and the term macrocycle is used for a ring containing more than a dozen atoms.
Cycloheptane, a non-aromatic cyclic compound.
Benzene, a cyclic compound.
Naphthalene, a polycyclic compound.
Porphyrin, a macrocyclic compound.
Pentazole, an inorganic cyclic compound.
Alicyclic compounds are named according to the IUPAC system of nomenclature by attaching the prefix cyclo- to the name of the corresponding open chain hydrocarbon possessing the same number of carbon atoms. The common names resemble the IUPAC names. For example: Cyclo pentane, cyclo butane etc....
Ring-closing & opening reactions 
Related concepts in organic chemistry are so-called ring-closing reactions in which a cyclic compound is formed and ring-opening reactions in which rings are opened.
Examples of ring-closing reactions:
- Ring-closing metathesis
- Nazarov cyclization reaction
- Ruzicka large ring synthesis
- Dieckmann condensation
- Wenker synthesis
- Radical cyclization
Example of ring-opening reactions:
- A general type of polymerization reaction: Ring-opening polymerization
- Ring opening metathesis polymerisation
See also 
- Polycyclic Compounds at the US National Library of Medicine Medical Subject Headings (MeSH)
- Macrocyclic Compounds at the US National Library of Medicine Medical Subject Headings (MeSH)