The communion of saints, when referred to persons, is the spiritual union of the members of the Christian Church, living and the dead, but excluding the damned. They are all part of a single "mystical body", with Christ as the head, in which each member contributes to the good of all and shares in the welfare of all.
Revelation 5:8 presents the saints in heaven as linked by prayer with their fellow Christians on earth.
In ecclesiology, the Christian Church is what different Christian denominations conceive of as being the true body of Christians or the original institution established by Jesus Christ. "Christian Church" has also been used in academia as a synonym for Christianity, despite the fact that it is composed of multiple churches or denominations, many of which hold a doctrinal claim of being the "one true church" to the exclusion of the others.
Medieval illustration of the ecclesia from the Hortus deliciarum of Herrad of Landsberg (12th century)
An Eastern icon depicting the Descent of the Holy Spirit. The date of Pentecost is considered the "Birthday of the Church".
An icon depicting Constantine I, accompanied by the bishops of the First Council of Nicaea (325), holding the Niceno–Constantinopolitan Creed of 381.
The Church is the congregation of saints, in which the Gospel is rightly taught and the Sacraments are rightly administered. –Augsburg Confession
