Proteus (/ - /,; Ancient Greek: Πρωτεύς, Prōteus) is a sea-god or god of rivers and oceans In Greek mythology. It is one of several gods which Homer calls the "Old Man of the Sea" (halios gerôn).
Proteus can change form, and only answers those who can capture him. From this comes the adjective protean, meaning "versatile", "changeable", or "capable of assuming many forms". "Protean" suggests flexibility, versatility and adaptability.