What is the definition of the church?

from the old testament

• Israel was chosen to be God’s covenant people, set apart to worship Him, obey His commands, and represent Him to the nations (Exodus 19:5–6; Deuteronomy 7:6). Leadership through priests, prophets, and elders shows a community organized around God’s Word and presence, with roles for teaching, serving, and guiding the people (Exodus 18:13–27; Numbers 11:16–17; Deuteronomy 1:9–18). These patterns foreshadow the New Testament church, as a gathered body of believers called out to worship, serve, and follow Christ under godly leadership.

from the new testament

• The word "church" comes from the Greek word ekklesia. Ekklesia means "a gathering, assembly" and is the basis for our word "congregation." And that is what God designed the church to be—a group of people.
• The definition of a "church" as a separate building specifically for worship would have been foreign to the early believers, as they met in homes. When a building was mentioned in the New Testament, it was always in relation to the church that met there (Romans 16:5; 1 Corinthians 16:19; Colossians 4:15; Philemon 1:2).
• Christ is the head of the church, and the church is the body of Christ (Ephesians 1:22–23).
• The members of the body of Christ are all Christians: "For just as the body is one and has many members, and all the members of the body, though many, are one body, so it is with Christ. For in one Spirit we were all baptized into one body—Jews or Greeks, slaves or free—and all were made to drink of one Spirit. For the body does not consist of one member but of many" (1 Corinthians 12:12–14). The universal church is defined as all who have received the Holy Spirit, no matter their location, denomination, or era. To ensure order and to provide fellowship, the universal church is also divided into local churches.
• The universal church is the body of Christ, composed of everyone who has received Christ as their Savior. It is comprised of every believer from every country and every time from Pentecost (Acts 2) until Christ's return.

implications for today

The church has always been the people, not the building. With the legitimization and affluence of Christianity in later years, the "church" came to mean the building where people met. Now, it is often used to mean a particular denomination. But the truest meaning of the word "church" is the group of believers. The universal church recognizes no denominations, just individual believers joined together in one body. No matter the denomination or the size of a local church, the purpose is to do corporately what all who name the name of Jesus are to do individually: glorify God in worship, obey and honor Him in all we do, and encourage one another to do the same.

The church is not a building; it is a group of people. It is not a denomination; it is everyone who has received the Holy Spirit. And it doesn't grant salvation; it is people, loving and glorifying God and teaching others about a saving knowledge of Christ. As believers, we are joined with all Christians, from Peter to the smallest child in the body of Christ. The local church is where the members of the universal church can apply 1 Corinthians 12 by encouraging, teaching, and building one another up in the knowledge and grace of the Lord Jesus Christ.