Ecclesiology

Sister Churches is a term used in 20th-century ecclesiology to describe ecumenical relations between the Roman Catholic Church and the Eastern Orthodox Churches, and more rarely and unofficially, between the Roman Catholic Church and the Anglican communion.

Ecumenism refers to efforts by Christians of different church traditions to develop closer relationships and better understandings.

Caesaropapism /ˌsiːzəroʊˈpeɪpɪzəm/ is the idea of combining the power of secular government with the religious power, or making it superior to the spiritual authority of the Church; especially concerning the connection of the Church with government.

The Christian Church is a term used by some to refer to the whole group of people belonging to the Christian religious tradition throughout history.

Presbyterian (or presbyteral) polity is a method of church governance ("ecclesiastical polity") typified by the rule of assemblies of presbyters, or elders.

"Pentarchy" (from the Greek Πενταρχία, Pentarchia from πέντε pente, "five", and ἄρχειν archein, "to rule") is a model historically championed in Eastern Christianity as a model of church relations and administration.

Apostasy in Christianity is the rejection of Christianity by someone who formerly was a Christian.

The word catholic (with lowercase c; derived via Late Latin catholicus, from the Greek adjective καθολικός (katholikos), meaning "universal") comes from the Greek phrase καθόλου (katholou), meaning "on the whole", "according to the whole" or "in general", and is a combination of the Greek words κατά meaning "about" and ὅλος meaning "whole".

In the Christian churches, holy orders are ordained ministries such as bishop, priest or deacon.

The word diocese is derived from the Greek term διοίκησις meaning "administration".

The Four Marks of the Church is a term describing four specific adjectives — one, holy, catholic and apostolic — indicating four major distinctive marks or distinguishing characteristics of the Christian Church.

Christendom has several meanings.

In several of the autocephalous Eastern Orthodox churches and Eastern Catholic Churches, the patriarch or head bishop is elected by a group of bishops called the Holy Synod.

The Handbook (formerly the Church Handbook of Instructions and earlier the General Handbook of Instructions) is a two-volume book of instructions and policies for leaders of The Church of Jesus Christ of Latter-day Saints (LDS Church).