From ek (out of) + kaleō (to call) — the 'called-out ones,' an assembly or gathering. In secular Greek, it was a political assembly of citizens. The NT adopted it for the community of believers, both local congregations and the universal body of Christ.
The ekklēsia is not a building but a people — those called out of darkness into God's light. Jesus declared, 'I will build my ekklēsia, and the gates of hell will not prevail against it' (Matthew 16:18). Paul describes it as Christ's body (1 Corinthians 12), His bride (Ephesians 5), and God's temple (1 Corinthians 3). The church is where heaven's life manifests on earth through worship, fellowship, and mission.