When the word “church” is found in the New Testament, it almost always comes from the Greek word ekklesia (in the KJV, Acts 19:37 is the only time the word “church” is translated from another word).
The vast majority of the time ekklesia is used in the New Testament, the word is translated “church,” and refers specifically to a “called out” assembly of people who are in Christ.
The word “church” is one term among several that describes the collective body of those who are in Christ.
In 1 Timothy 3:15, the church is called “the house of God” (i.e., household or family of God). In Ephesians 2:21, the church is called “a holy temple in the Lord.” In Ephesians 1:23, the church is referred to as Christ’s “body.”
Though several terms are used to describe the church, they are not “denominations” of the Lord’s body. Rather, multiple terms are used to describe the same body. Just as Jesus may be called “Lord,” “Savior,” “Christ,” “King,” “Redeemer,” “Prophet,” “High Priest,” etc., “the church” may be called “church of Christ,” “church of God,” “kingdom of Christ,” “family of God,” “temple of the Lord,” “body of Christ,” etc.
Ephesians 4:4 makes it clear that these terms all refer to just one church, as it states, “There is one body.”
Having said this, there are times Scripture uses the word “churches” in the plural form (Rom. 16:16; Gal. 1:2).
The reason for this is that while the church is sometimes referred to in the “universal” sense (all Christians throughout the world), it is at other times referred to in the “local” sense (Christians who meet together at a particular location to carry out the work of the church). The distinction between different “churches” in Scripture is not what doctrine they are to follow or who their source of authority is. Rather, they are distinguished from one another by location. The apostle Paul wrote to the church “at Corinth” (1 Cor. 1:2; 2 Cor. 1:1). He wrote to saints “at Ephesus” (Eph. 1:1), “at Philippi” (Phil. 1:1), and “at Colosse” (Col. 1:2). He referenced a church that was “of the Thessalonians” (1 Thess. 1:1; 2 Thess. 1:1), but this again identified their location. Doctrinally, this church was “in God the father and in the Lord Jesus Christ” (1 Thess. 1:1; cf. 2 Thess. 1:1).
This was true of all local churches in the New Testament. None were identified as belonging to a fallible man. Rather, each one belonged to God and Christ (1 Cor. 1:2; 2 Cor. 1:1; Eph. 1:1; Phil. 1:1; Col. 1:2).
This is the core factor that unifies Christians. Those in the Lord’s body find unity by looking to the same Head, who has given us the same message and is the Savior of us all.
The “one body” (Eph. 4:4) is “His body” (Eph. 1:23). Colossians 1:18 says, “He is the head of the body, the church: Who is the beginning, the firstborn from the dead; that in all things He might have the preeminence.”
Unity is found by heeding the Head’s authoritative instruction. As God the Father said in Matthew 17:5, “This is my beloved Son, in Whom I am well pleased; hear ye Him.” In the religious world, there is a diversity of doctrines and creeds. In Christ, there is unity.
– Michael Hickox