By definition it’s “the called out”. Meaning called out of the world to be a special people to God. Titus 2:14 and 1 Peter 2:9.
In the New Testament there was ONLY ONE. There were no denominations ( meaning divisions) for almost 600 years. The Catholic Church has the distinction (?) of being the first denomination to disregard Jesus’s prayer for unity in John 17. I believe it was about 590 when Gregory was declared the first Pope. There was no way Peter could have been a pope when the Catholic Church was not even in existence for 500 years.
Jesus calls his “body” the church Colossians 2:24 and Colossians 1:18. Then in Ephesians 4:4 Paul says there is ONE BODY….therefore, there is one church. It’s the only one that Jesus promised to build in Matthew 16:18.
What is the church? Well, there are over 400 different sects of Christianity; all teaching different things, practicing different things and often contradicting each other. Kinda makes it hard to define the word “church” by man’s standards. However, a very clear picture of the church emerges when you take every passage about the church in the New Testament and put them all together.
Although there was just “one body”, there were many congregations of that “one body” in the first century.
Paul wrote letters to the churches of Galatia, the church at Corinth, and Thessalonica. Many letters were just addressed to Christian’s at various cities, but I’m sure there would have been churches there if there were Christian’s there. So, many, many churches in tge New Testament but all