The term used for the group of believers is ekklesia. In pre-Christian usage, ekklesia refers to any gathering of a group of people, even a gathering of an army in preparation for war or a coming together of an unruly crowd. In the Christian, especially Paul’s, usage of the term, ekklesia refers to a gathering of Christians who came together as a regularly constituted group. Paul adds other words like “in God the Father” or “in the Lord Jesus” which mark the Christian ekklesia not merely as a human association, a gathering of like-minded individuals for a religious purpose, but a divinely-created affair.
There were no buildings for worship in early Christianity. Christians would gather together in a house, and this gathering was called oikos-ekklesia or “house-church.” When Paul wrote letters to individual Christians, he would also greet the ekklesia in their house (1 Cor 16:19). The church would probably be composed of the head of the house and his extended family, including slaves. Ekklesia would also refer to a group of families or neighbors living and working in close proximity with one another, probably worshipping together.
The size of the early Christian house-church was probably not big. The average membership was around thirty people. That of the domestic group would have been much smaller. The church was small enough for a relatively intimate relationship.
