Ribosyl or deoxyribosyl derivatives (rarely, other glycosyl derivatives) of certain pyrimidine or purine bases. They are thus glycosylamines or N-glycosides related to nucleotides by the lack of phosphorylation. It has also become customary to include among nucleosides analogous substances in which the glycosyl group is attached to carbon rather than nitrogen ('C-nucleosides').
See also: nucleic acids
PAC, 1995, 67, 1307. 'Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)' on page 1352 (https://doi.org/10.1351/pac199567081307)