cyclo-

  1. A prefix used in names to designate a ring structure, usually italicized in inorganic, but not in organic nomenclature. Examples:
    C01495-1
    C01495-2
    Source:
    Red Book, p. 245
    Blue Book, p. 497
    See also:
    Blue Book (Guide), p. 30
  2. 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.
    Source:
    PAC, 1989, 61, 23 (System for symbolic representation of reaction mechanisms (Recommendations 1988)) on page 34