The Baptist Church, the Lutheran Church, the Catholic Church, The Church of Jesus Christ of Latter-day Saints, the church of the devil, the church of the [F]irstborn, the Church…
The word “church” is often used to refer to either concrete or abstract entity: a building for religious service (Merriam-Webster definition 1, “we’ll meet at the church”) or a formal organization (ie. “the articles of faith of the church”). But for either, the church is something exterior and formalized.
The word “church” appears 115 times in the King James translation of the New Testament. There is but a single Greek word from which these instances are translated – ἐκκλησία, transliterated ekklesia. That is translated simply as a gathering or assembly. Originally, it was the term used for Athens’ principle democratic assembly. It is easy, and happens not infrequently, that a place comes to be called by the purpose or meeting there. “I went to court this morning” rather than “I went to the court building this morning” would not be unnatural. But the place is the court building, the building for the court. The court is the members of the body, just as the church, the ekklesia, is the gathering of the members of that body.
The Baptist Church is the assembly or gathering of Baptists, same with the Lutheran, Catholic, and down the line. Or it could be said that a member of Baptists is in assembly with [other] Baptists. When one is a member of a particular church, it is similar to being a member of a neighborhood, a board, or a committee. The committee is not some self-existent entity, but exists in the gathering of its members.
This is especially enlightening towards two of the churches listed at the beginning – the church of the devil and the church of the Firstborn. The church of the devil is, from above, those assembled with the devil; the church of the Firstborn is those assembled with the Firstborn.
Now ye are the body of Christ, and members in particular. – 1 Corinthians 12: 27