The actual word doesn't appear in the bible as it derives from a Latin word and the bible was written in Hebrew and Greek. The actual idea of a trinity appears in several places.
Zero! Nada! Zilch!
The trinity is a fabrication
Trinity is not a word which Jesus used, it is not even found in the Bible, but it is used to describe what we know about God. Christianity stands or falls by what the doctrine says.
The Doctrine of the Trinity:
1st: God eternally exists as three persons, Father, Son, and Holy Spirit,
2nd: Each person is fully God
3rd: There is one God.
The doctrine of the Trinity is not an invention of men, nor is it an addition to the Bible. The Trinity is a crystallization of the teachings of the Bible. Some verses related to the Trinity in the New Testament.
John 5:23 that all may honor the Son just as they honor the Father. He who does not honor the Son does not honor the Father, who sent him.
2 Peter 1:17 For he received honor and glory from God the Father when the voice came to him from the Majestic Glory, saying, "This is my Son, whom I love; with him I am well pleased." 18 We ourselves heard this voice that came from heaven when we were with him on the sacred mountain.
1 John 1:3 We proclaim to you what we have seen and heard, so that you also may have fellowship with us. And our fellowship is with the Father and with his Son, Jesus Christ.
The doctrine of the Trinity is a difficult subject to understand even to many Christians. This proves that the Bible is indeed God's word and Christianity is not man-made. After all who would invent a religion which is complicated and difficult to comprehend?