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Definition

noun, plural: nucleosides

(1) A nitrogenous base (purine or pyrimidine) bound to a pentose sugar ribose or deoxyribose.

(2) A glycoside formed from the hydrolysis of nucleic acid.

Supplement

A phosphate group attached to a nucleoside would make a nucleotide.

Depending on the pentose sugar component, a nucleoside may be a ribonucleoside (e.g. adenosine, guanosine, cytidine, and uridine) or a deoxyribonucleoside (e.g. deoxyadenosine, deoxyguanosine, deoxycytidine, deoxythymidine).

Word origin: nucleic- from nucleus + -ose + -ide.

Related terms: nucleoside analogue, nucleoside diphosphate.

Compare: nucleotide.
See also: nucleic acid.