Ecumenism

Ecumenism derives from the Greek adjective oikoumenikos (ecumenical) and the noun oikoumenē, the latter term employed since the time of Herodotus (5th century B.C.E.) to mean "the inhabited earth" or "the whole world." Oikoumenē then came to refer specifically to the realm of the Greco-Roman empire and its culture as distinguished from so-called barbarian lands and cultures. During the fourth century C.E., oikoumenē took on the combined political-religious meanings of "the one Christian empire" or "the unified Christian world."