A compound of importance in physiological and medical research, obtained during partial decomposition (hydrolysis) of nucleic acids and containing a purine or pyrimidine base linked to either d-ribose, forming ribosides, or d-deoxyribose, forming deoxyribosides. They are nucleotides minus the phosphorus group.See Adenosine; Cytidine; Guanosine; Uridine.