Now about that time Herod the king stretched forth [his] hands to vex certain of the church.
Note 1 at Ac 12:1: The word "church" comes from the compound Greek word "EKKLESIA," and this Greek word means "calling out" ("EK" - "out" and "KALEO" - "to 'call'") (Strong's Concordance). The word EKKLESIA, technically, could identify any assembly, like how it was used in Ac 19:39 to refer to a town assembly and in Ac 7:38 to refer to the assembly of Israelites who came out of Egypt. However, the word is typically used to distinguish those who, through faith in Christ, have been called out of the world into the kingdom of God.
The word "church" identifies the body of Christ as a whole (Mt 16:18; Col 1:18, and 24) and can also refer to a local part of the body of Christ (Ro 16:5; 1Co 1:2; Re 2:1, 8, 12, and 18). Nowhere in Scripture does it refer to a building that the saints meet in. The church is not brick and mortar but born-again people. The only scriptural reason for different assemblies, or churches, is location. Doctrinal differences were meant to be resolved (1Co 1:10) and are not a justification for division in the universal church.