
The First Council of Nicaea was a council of Christian bishops convened in the Bithynian city of Nicaea (now ?znik, Bursa province, Turkey) by the Roman Emperor Constantine I in 325 AD. Its main accomplishments were settlement of the Christological issue of the divine nature of God the Son and his relationship to God the Father, the construction of the first part of the Nicene Creed, establishing uniform observance of the date of Easter, and promulgation of early canon law.

The Christian doctrine of the Trinity (Latin: trinus "threefold") holds that God is one God, but three coeternal consubstantial persons or hypostases. These being the Father, the Son (Jesus Christ), and the Holy Spirit - as "one God in three Divine Persons". The three Persons are distinct, yet are one "substance, essence or nature" (homoousios).

A church is a building used for Christian worship services and Christian activities. The earliest identified Christian church is a house church founded between 233 AD and 256 AD. The word church also describes a body or assembly of Christian believers, while "the Church" refers to the worldwide Christian religious community.