Monergism

“There is one only and true God, but in the unity of the Godhead there are three coeternal and coequal Persons, the same in substance but distinct in subsistence.
- B.B. Warfield

The Trinity: God eternally exists as three persons, Father, Son and Holy Spirit, and each person is fully God, and there is one God. -Wayne Grudem

In no other subject is error more dangerous, or inquiry more laborious, or the discovery of truth more profitable. - Augustine De Trinitate 1.3.5

"Your father Abraham rejoiced to see My day, and he saw it and was glad." The Jews therefore said to Him, "You are not yet fifty years old, and have You seen Abraham?" Jesus said to them, "Truly, truly, I say to you, before Abraham was born, I am." Therefore they picked up stones to throw at Him; but Jesus hid Himself, and went out of the temple. - John 8:58

Trinity. The term designating one God in three persons. Although not itself a biblical term, "the Trinity" has been found a convenient designation for the one God self-revealed in Scripture as the Father, Son, and Holy Spirit. It signifies that within the one essence of the Godhead we have to distinguish three "persons" who are neither three gods on the one side, nor three parts or modes of God on the other, but coequally and coeternally God. (Evangelical Dictionary of Theology, Walter Elwell--Editor, p.1112)