The Bible from verse one in the Book of Genesis, is very clear that "God" is not One "Person". The Hebrew "Elohim", is in the masculine gender, and plural in number, "el" being the singular. In Genesis 1:26, we read, "Let US make humans in OUR Image and after OUR likeness". In both the Old and New Testaments, there are Three Who are equally called Yahweh/God. The Father, the Son, and the Holy Spirit. In Isaiah 48:16, the Speaker is Yahweh, Who is the Creator, He here speaks of being sent by Another, Who is "Yahweh Adoni", Who also also sends the Holy Spirit.
The term Holy Trinity is used to describe how the God of the Holy Bible can be One, and at the same time, Three Persons, as in 1x1x1, which is 1; not 1+1+1, which is 3! There is not other way to understand this Mystery. Just because "Trinity" is not used in the Bible, does not mean that it is man-made and not Biblical. The term Incarnation is not in the Bible, but yet is is clear that it is very much taught in the Bible. As are the terms Theophany and Christophany, both not in the Bible, but teach what is in the Bible!