A prefix used in names to designate a ring structure, usually italicized in inorganic,
but not in organic nomenclature. Examples:
See also: Blue Book (Guide), p. 30
The prefix for an elementary reaction or some part thereof indicating that the bonds undergoing primitive changes form
part of a ring in the transition state of a pericyclic process.
PAC, 1989, 61, 23
(System for symbolic representation of reaction mechanisms (Recommendations 1988))
on page 34