Nucleosides

When a base is linked to a 5-carbon sugar (pentose) through a C-N bond (β-glycosidic bond) with the loss of a water molecule, the resulting compound is called a nucleoside. A base linked to a ribose sugar is called a riboside (adenine forms adenosine), and when the sugar is deoxyribose, it is called a deoxyriboside.

Nucleotides

Nucleotides are phosphate esters of nucleosides. The phosphoric acid is bound to the –CH₂ OH group of the sugar molecule by an ester bond. The compound thus formed is called a monophosphate of the base.