Nontrinitarian or antitrinitarian beliefs concerning God deny that God is a Trinity. These terms have no meaning except in contrast to the Christian doctrine of God as agreed upon in the first six ecumenical councils of the Catholic Church.
Denial of trinitarian belief by self-described Christians does not necessitate denial of the deity of Jesus Christ, although that is one alternative found among Unitarians, for example. Modalist Monarchianism (which states that the Father, Son, and Holy Spirit are modes, or manners of God's self-expression) asserts that the Son is one mode of revelation by which the one God has been made known. An example of a Modalist Monarchian would be a Oneness Pentecostal. Other, various, nontrinitarian alternatives include the Christadelphians, Jehovah's Witnesses, and the Church of Jesus Christ of Latter-day Saints.
See also: Heresy.