In the polynucleotide chain of DNA, a nitrogenous base is linked to the –OH of

In a polynucleotide chain, a nitrogenous base is linked to the OH of 1' C pentose sugar through a N-glycosidic linkage to form a nucleoside. 

When a phosphate group is linked to OH of 5' C of a nucleoside through phosphoester linkage, a corresponding nucleotide (or deoxynucleotide depending upon the type of sugar present) is formed. 

Two nucleotides are linked through 3'-5' phosphodiester linkage to form a dinucleotide.