Both are nucleotides, serving as the monomers of RNA and DNA, respectively. Another similarity is that both form phosphodiester bonds through the 5’-3’ direction, connecting with another nucleotide to build the polynucleotide chain. They also both consist of three essential components: a nitrogenous base (Adenine, Guanine, or Cytosine), a pentose sugar (ribose or deoxyribose), and a phosphate group.