Trinity

The Christian doctrine that God is one being in three persons: Father, Son, and Holy Spirit. It distinguishes the persons without dividing the one God.

Divine essence: The nature or being understood as belonging to God. The doctrine distinguishes the one divine essence from the three persons.
First Council of Nicaea: A Christian council held in 325 that rejected Arian teaching and affirmed the Son’s relation to the Father. It established a foundational creed and vocabulary for Trinitarian debate.
Unitarianism: A Christian theological tradition that rejects the doctrine of God as three coequal persons. It represents a Christian alternative that denies the Trinity’s central formulation.
Baptism: A Christian rite involving water that marks entry into the community of faith. Many churches baptize with a formula naming the Father, Son, and Holy Spirit.
Hypostasis: A Greek term for an individually subsisting reality, used in Christian theology for a divine person. It became a technical term for the Father, Son, and Holy Spirit as distinct persons.
First Council of Constantinople: A Christian council held in 381 that reaffirmed Nicaea and clarified teaching about the Holy Spirit. Its creed extended the doctrinal formula to the Spirit’s divinity.
Modalism: A theological position that treats Father, Son, and Holy Spirit as modes or manifestations of one divine person. It preserves divine oneness by denying the lasting personal distinctions affirmed by Trinitarian doctrine.
Doxology: A short expression of praise to God, often used in Christian worship. Trinitarian doxologies direct praise to the Father, Son, and Holy Spirit.
Homoousion: A Greek term meaning “of the same substance,” used to affirm the Son’s full divinity with the Father. The term expresses the shared divine nature of Father and Son.
Arianism: A fourth-century Christian theological position that treated the Son as created and subordinate to the Father. Its claims prompted decisive defenses of the Son’s full divinity.

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