The word catholic with lowercase c; derived via Late Latin catholicus, from the Greek adjective katholikos, meaning “universal” comes from the Greek phrase katholou, meaning “on the whole”, “according to the whole” or “in general”, and is a combination of the Greek words meaning “about” and meaning “whole”. The term Catholic (usually written with uppercase C in English) was first used to describe the Christian Church in the early 2nd century to emphasize its universal scope. In the context of Christian ecclesiology, it has a rich history and several usages.
The word in English can mean either “of the Roman Catholic faith” or “relating to the historic doctrine and practice of the Western Church”. Many Christians use it to refer more broadly to the whole Christian Church or to all believers in Jesus Christ regardless of denominational affiliation; it can also more narrowly refer to Catholicity, which encompasses several historic churches sharing major beliefs. “Catholicos”, the title used for the head of some churches in Eastern Christian traditions, is derived from the same linguistic origin.