* Ionic Character: Nickel (Ni) is a metal, and sulfur (S) is a nonmetal. Metals tend to lose electrons and become positively charged ions (cations), while nonmetals tend to gain electrons and become negatively charged ions (anions). This difference in electronegativity leads to an electrostatic attraction between the Ni²⁺ and S²⁻ ions, which is the basis of ionic bonding.

* Covalent Character: The difference in electronegativity between nickel and sulfur is not huge. This means that there is also some sharing of electrons between the nickel and sulfur atoms, contributing to a degree of covalent character.

In summary, nickel sulfide is best described as having a mixed ionic-covalent bonding character. The bond is primarily ionic but has a significant degree of covalent character as well.