The word "trinity" isn't used in the Bible but a word used to describe what is apparent about God in the Scriptures. The Bible also states that there is One God. That's where the word trinity comes from Tri + Unity = Trinity.
Here is some scripture that shows God is one, in trinity: (look it up at Bible Gateway)
Deut 6:4
Isa. 45:5
1Cor. 8:4
Matt. 3:16-17
Matt. 28:19
John 10:30 Jesus said "I and the Father are one."
John 14:9
Rom. 8:9 If anyone does not have the Spirit of Christ, he does not belong to him.
Matt 1:20 "Joseph, son of David, do not be afraid to take Mary as your wife; for that which has been conceived in her is of the Holy Spirit."
