Here's why:

* Electronegativity: Boron has an electronegativity of 2.04, while nitrogen has an electronegativity of 3.04. The difference in electronegativity is significant, indicating that nitrogen attracts electrons more strongly than boron.

* Sharing of electrons: Instead of one atom completely taking an electron from the other, boron and nitrogen share electrons to form a stable bond. This sharing of electrons is the defining characteristic of a covalent bond.

Specifically, boron and nitrogen often form a coordinate covalent bond, where one atom (in this case, nitrogen) provides both electrons for the shared pair.

Examples:

* Borazine (B3N3H6): This compound is often called "inorganic benzene" due to its structural similarity to benzene. It contains alternating boron and nitrogen atoms linked by covalent bonds.

* Boron nitride (BN): This material exists in various forms, including hexagonal boron nitride (similar to graphite) and cubic boron nitride (similar to diamond). The bonds between boron and nitrogen in these structures are also covalent.