Here's why:

* Electronegativity: Phosphorus and sulfur have relatively similar electronegativity values. This means they have a similar ability to attract electrons.

* Sharing Electrons: Instead of one atom completely taking an electron from the other (ionic bonding), phosphorus and sulfur share electrons to achieve a stable electron configuration.

Examples of Compounds:

* Phosphorus pentasulfide (P₂S₅): This compound has covalent bonds between phosphorus and sulfur atoms.

* Phosphorus sesquisulfide (P₄S₃): Another compound with covalent bonds between phosphorus and sulfur.

Note: While the bond is generally considered covalent, there can be a slight polar character due to the small difference in electronegativity between phosphorus and sulfur.