Trinity is a word that describes three things together as one, three in concert, one divided into three or manifested as three. By definition the word 'trinity' is in the Scriptures. Listed below are a few of the trinities found in Scripture.
The two trinities that are against man:
1 John 2:16 For all that is in the world, the lust of the flesh, and the lust of the eyes, and the pride of life, is not of the Father, but is of the world.
Revelation 20:10 The Devil, the beast, the false prophet
The trinity that over comes evil:
1 Corinthians 13:13 Faith, Hope and Charity
Whether or not a particular word is found or not found in the Scriptures is not an issue. The issue is and always will be, "What sayeth the Scripture". Does what you say or describe conform, coincide and correspond with the word of God.
The following is a list of some of the many references found in the Scriptures that show that Jesus Christ was the one and only God manifested in the flesh and that the God of the Bible is to be understood as a trinity.
John 1:1 In the beginning was the Word, and the Word was with God, and the Word was God.
John 1:14 And the Word was made flesh, and dwelt among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth.
1 Timothy 3:16 And without controversy great is the mystery of godliness: God was manifest in the flesh, justified in the Spirit, seen of angels, preached unto the Gentiles, believed on in the world, received up into glory.
2 Corinthians 5:19 To wit, that God was in Christ, reconciling the world unto himself, not imputing their trespasses unto them; and hath committed unto us the word of reconciliation.
1 John 5:7 For there are three that bear record in heaven, the Father, the Word, and the Holy Ghost: and these three are one. (see #2)
John 10:30 I and my Father are one.
John 14:8-9 Philip saith unto him, Lord, show us the Father, and it sufficeth us. 9Jesus saith unto him, Have I been so long time with you, and yet hast thou not known me, Philip? he that hath seen me hath seen the Father; and how sayest thou then, Show us the Father?
John 19:37 And again another scripture saith, They shall look on him whom they pierced.
Revelations 1:7 Behold, he cometh with clouds; and every eye shall see him, and they also which pierced him: and all kindreds of the earth shall wail because of him. Even so, Amen.
Zechariah 12:4-10 In that day, saith the LORD,... 10..and they shall look upon me whom they have pierced, and they shall mourn for him, as one mourneth for his only son, and shall be in bitterness for him, as one that is in bitterness for his firstborn.
Philippians 2:10 That at the name of Jesus every knee should bow, of things in heaven, and things in earth, and things under the earth;
Isaiah 45:23 I have sworn by myself, the word is gone out of my mouth in righteousness, and shall not return, That unto me every knee shall bow, every tongue shall swear.
We see here in the above verses that the Lord of the Old Testament is the one that gets pierced, which is a reference to the crucifixion and that he is the God of the Old Testament where which every knee shall bow.
Acts 20:28 Take heed therefore unto yourselves, and to all the flock, over the which the Holy Ghost hath made you overseers, to feed the church of God, which he hath purchased with his own blood.
Revelations 1:5 And from Jesus Christ, who is the faithful witness, and the first begotten of the dead, and the prince of the kings of the earth. Unto him that loved us, and washed us from our sins in his own blood,
Isa 44:6 Thus saith the LORD the King of Israel, and his redeemer the LORD of hosts; I am the first, and I am the last; and beside me there is no God.
Revelations 1:8 I am Alpha and Omega, the beginning and the ending, saith the Lord, which is, and which was, and which is to come, the Almighty.
Revelations 1:11 Saying, I am Alpha and Omega, the first and the last:
Revelations 2:8 And unto the angel of the church in Smyrna write; These things saith the first and the last, which was dead, and is alive;...
Isaiah 9:6 For unto us a child is born, unto us a son is given: and the government shall be upon his shoulder: and his name shall be called Wonderful, Counsellor, The mighty God, The everlasting Father, The Prince of Peace.
We see again that Jesus and the Lord and God of the OT are one and the same.
Micah 5:2 But thou, Bethlehem Ephratah, though thou be little among the thousands of Judah, yet out of thee shall he come forth unto me that is to be ruler in Israel; whose goings forth have been from of old, from everlasting.
Isaiah 9:6 KJV For unto us a child is born, unto us a son is given: and the government shall be upon his shoulder: and his name shall be called Wonderful, Counsellor, The mighty God, The everlasting Father, The Prince of Peace.
Matthew 16:16-17 And Simon Peter answered and said, Thou art the Christ, the Son of the living God. 17And Jesus answered and said unto him, Blessed art thou, Simon Barjona: for flesh and blood hath not revealed it unto thee, but my Father which is in heaven.
Luke 4:41 And devils also came out of many, crying out, and saying, Thou art Christ the Son of God. And he rebuking them suffered them not to speak: for they knew that he was Christ.
John 6:69 And we believe and are sure that thou art that Christ, the Son of the living God.
John 5:18 Therefore the Jews sought the more to kill him, because he not only had broken the sabbath, but said also that God was his Father, making himself equal with God.
Philippians 2:5-6 Let this mind be in you, which was also in Christ Jesus: 6Who, being in the form of God, thought it not robbery to be equal with God:
We see, comparing the Old with the New Testament, in the above verses that the Lord of the Old Testament and the Lord Jesus Christ are both the eternal God.
Gen 1:1 In the beginning God created the heaven and the earth.
John 1:10 He was in the world, and the world was made by him, and the world knew him not.
Col 1:16 For by him were all things created, that are in heaven, and that are in earth, visible and invisible, whether they be thrones, or dominions, or principalities, or powers: all things were created by him, and for him:
It seems difficult for me not to understand the Bible is teaching that Jesus Christ was God manifested in the flesh. Much of the trouble arising with the doctrine of the Trinity is that many attempts to provide a description of it that they could not possibly show, going far beyond what is revealed concerning it within the Scriptures. I do not see where it defines God as three completely different personages, or in any way other than there is three in some form or fashion. However, God is constituted does not affect the fact that Jesus was God.
I am sure that this list is by no means complete, but I hope that it will help you in your defense of the faith. If nothing else it does show that the doctrine of the trinity is derived from the Scriptures and that Christ was God manifested in the flesh which some have tried to deny.