cyclo-

https://doi.org/10.1351/goldbook.C01495
  1. A prefix used in names to designate a ring structure, usually italicized in inorganic, but not in organic nomenclature. Examples:
    C01495-1.png
    C01495-2.png
    Sources:
    Blue Book, p. 497 (http://www.acdlabs.com/iupac/nomenclature/)
    Red Book,3rd ed., p. 245 (https://doi.org/10.1515/pac-2014-0718)
    See also:
    Blue Book Guide, p. 30 (https://doi.org/10.1351/pac199971071327)
  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 (https://doi.org/10.1351/pac198961010023)