Hence we call the ester as phosphodiester, as a single phosphoric acid is linked to two sugars present on different nucleotides. Thus, the bond is called as phosphodiester bond.

To be precise, we should call this bond as 3'-5 ' phosphodiester bond so that there is no confusion about which carbon atoms in the sugar participate in the bond. Up to three individual phosphate groups can be attached in series giving a nucleotide monophosphate (NMP), nucleotide diphosphate (NDP) and nucleotide triphosphate (NTP). The individual phosphate groups are designated α, β and γ with the α phosphate being the one attached directly to the sugar.