Nitrogenous base molecule is joined to sugar molecule by a glycosidic bond and forms a structure called nucleoside.
The nucleoside combines with a phosphate group by an ester bond to form a nucleotide.
A unit formed by the attachment of a base of 1' position of sugar is known as nucleoside when nucleoside is linked to phosphoric acid at 5' position of sugar moiety we get a nucleotide.
