Monomer of nucleic acid is Nucleotide.
Nucleotide is made up of three components namely- Nitrogenous base, pentose suger and phosphate group.
Depending upon the nucleic acid,i.e RNA or DNA, nucleotide can be Ribonucleoside triphosphate (rNTP) and deoxyribonucleoside triphosphate repectively (dNTP).