The type of bond that occurs between nitrogenous bases in DNA and RNA is a hydrogen bond.

Here's why:

* Hydrogen bonds are weak bonds that form between a hydrogen atom covalently linked to a highly electronegative atom (like oxygen or nitrogen) and an electron pair in the adjacent atom.

* Nitrogenous bases contain functional groups with hydrogen bond donors (like N-H) and acceptors (like O or N).

* These complementary base pairs (Adenine-Thymine/Uracil and Guanine-Cytosine) form specific hydrogen bond pairings, which contribute to the stability and structure of DNA and RNA.

Let me know if you'd like more details on the specific hydrogen bonding patterns within the base pairs!