1. A prefix used in names to designate a ring structure, usually italicized in inorganic, but not in organic nomenclature. Examples:
    Blue Book, p. 497 [Terms] [Book]
    Red Book, 3rd ed., p. 245 [Terms] [Book]
    See also:
    Blue Book Guide, p. 30 [Terms] [Book]
  2. The prefix for an @[email protected] or some part thereof indicating that the bonds undergoing primitive changes form part of a ring in the @[email protected] of a @[email protected] process.
    PAC, 1989, 61, 23. (System for symbolic representation of reaction mechanisms (Recommendations 1988)) on page 34 [Terms] [Paper]