Nontrinitarianism

Nontrinitarianism refers to belief systems within Christianity which reject the mainstream Christian doctrine of the Trinity, namely, the teaching that God is three distinct hypostases or persons who are coeternal, coequal, and indivisibly united in one being, or essence (from the Greek ousia). Certain religious groups that emerged during the Protestant Reformation have historically been known as antitrinitarian.

According to churches that consider the decisions of ecumenical councils final, Trinitarianism was definitively declared to be Christian doctrine at the 4th-century ecumenical councils, that of the First Council of Nicaea (325), which declared the full divinity of the Son, and the First Council of Constantinople (381), which declared the divinity of the Holy Spirit.

In terms of number of adherents, nontrinitarian denominations comprise a small minority of modern Christianity. By far the three largest nontrinitarian Christian denominations are The Church of Jesus Christ of Latter-day Saints ("Mormons"), Jehovah's Witnesses and the Iglesia Ni Cristo, though there are a number of other smaller ones, including the Christadelphians, Christian Scientists, Dawn Bible Students, Living Church of God, Oneness Pentecostals, Members Church of God International, Unitarian Universalist Christians, The Way International, The Church of God International and the United Church of God.

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