Trinity

Trinity is from the Latin trinitas, a word coined or popularized by the second-century theologian Tertullian to express the Christian teaching that God is one in essence and three in persons[1]. The Greek equivalent is trias. The Latin term entered English through medieval Christian theology and has remained the standard label in English-speaking Christianity ever since[2].

The word itself is not in the Bible[2]. Christian theologians developed the term to summarize teachings drawn from scripture and from the worship and creedal language of the early church, especially in response to debates in the fourth and fifth centuries that produced the Nicene and Constantinopolitan creeds[1].

the Trinity is often misunderstood as either three gods or a simple metaphor, neither of which reflects classical doctrine well.

Trinitarian theology is shared across Catholic, Orthodox, and most Protestant Christianity[2]. The classical formulation is that God exists as one being (one ousia, one essence) in three persons (three hypostases or three personae): the Father, the Son (Jesus Christ), and the Holy Spirit[3]. These persons are co-eternal, co-equal, and distinct without being separate gods[3].

Christian worship is shaped by Trinitarian patterns. Baptism is performed in the name of the Father, Son, and Holy Spirit[4]. The Nicene Creed, recited weekly in many liturgies, is structured around the three persons[5]. Prayers often follow a Trinitarian pattern: to the Father, through the Son, in the Holy Spirit. The Eucharistic prayer and many hymns are Trinitarian in shape[2].

A small number of Christian groups reject Trinitarian doctrine, including Jehovah's Witnesses, The Church of Jesus Christ of Latter-day Saints (which holds a distinctive view of the Godhead), Unitarians, and Oneness Pentecostals[2]. These groups read the same biblical material differently and reach different conclusions about the relationship of Father, Son, and Holy Spirit[2].

Trinitarian theology is one of the most extensively developed areas of Christian thought[1]. The doctrine emerged through centuries of debate (against Arianism, Modalism, Tritheism, Subordinationism) and was formalized in the creeds of Nicaea (325 CE) and Constantinople (381 CE), with further refinement at Chalcedon (451 CE)[1]. Eastern Orthodox and Western Christian theology developed different emphases over time, with the filioque clause (the question of whether the Holy Spirit proceeds from the Father alone or from the Father and the Son) becoming a major point of difference[6]. Modern comparative theology has revisited Trinitarian doctrine in conversation with Jewish, Islamic, and Hindu thought about divine unity and plurality[2].

• The Christian Tradition: Volume 1by Jaroslav Pelikan
  book
• On the Trinityby Augustine of Hippo
  primary source