Though the word “Trinity” is not found anywhere in the Bible, the theology behind it is seen throughout. The Trinity does not follow logic, but we must understand that theology is not always logical. In mathematics 1+1+1=3, but in the Theology Proper 1+1+1=1. John Wesley once said, “Tell me how it is that in this room there are three candles but one light, and I will explain to you the Trinity.”
I believe in one Triune God, eternally existing in three persons—Father, Son, and Holy Spirit—co-eternal in being, co-identical in nature, co-equal in power and glory, and having the same attributes and perfections. (Duet.6:4). The Trinity is the doctrine that God is one essence in three co-eternal, co-equal persons (Mt. 3:13-17; Mt.28:19-20; Gen.1:1, 1:26; Jn.1:1, 20:28; Acts 5:3-4; 2 Cor.13:14).
The Bible clearly states that God is One (Ex.20:2-3; Duet.6:4; 1 Cor.8:4). I do not believe in Tri-theism (three separate Gods), but only one God. However, it is correct to say that there are three members of the Godhead. First, God the Father is God (Eph.1:3; 1 Cor.8:6). Second, God the Son is God (John 1:1-14; John 8:58; John 20:30-31; Phil.2:6-8). Third, God the Holy Spirit is God (Acts 5:3-5; 1 Cor.3:16). The Father, Son, and Holy Spirit are united together as One as is seen in the Great Commission (Mt.28:19-20) and the baptism of Jesus (Mt.3:13-17).
In conclusion, God eternally exists as three persons, Father, Son, and Holy Spirit, and each person is fully God, and there is one God. Broken down, this amounts to three propositions: God is three persons. Each person is fully God. There is one God. In addition, it’s helpful to elaborate on the fact that when we say, “God is three persons,” we mean that he is not just one person, and that the persons of the Trinity are not to be confused. So we can also say: The Father is God. The Son is God. The Holy Spirit is God. The Father is not the Holy Spirit, and the Holy Spirit is not the Father. The Holy Spirit is not the Son, and the Son is not the Holy Spirit. The Son is not the Father, and the Father is not the Son.
Justin Taylor, Trinity 101. http://www.desiringgod.org/Blog/869_trinity_101/