https://doi.org/10.1351/goldbook.T06279
Natural products and related compounds formally derived from isoprene units (see @I03306@). They contain oxygen in various functional groups. This class is subdivided according to the number of carbon atoms in the same manner as are @T06278@. The skeleton of terpenoids may differ from strict additivity of isoprene units by the loss or shift of a fragment, generally a methyl group.
Source:
PAC, 1995, 67, 1307. (Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)) on page 1371 [Terms] [Paper]
See also:
White Book, 2nd ed., p. 255 [Terms] [Book]