Adonai, in Hebrew, denotes Master (Gen. 15:2, 8; Exo. 4:10; cf. Gen. 24:9, 10, 12) and Husband (cf. Gen. 18:12). In Genesis 24 Abraham's old servant called Abraham his master. A slave has a lord, and that lord is his master, his owner, his possessor. In Genesis 18:12, Sarah referred to Abraham as her lord. The husband is the lord to the wife, and the lord is the master. On the one hand, our God is our Master. On the other hand, our God is our Husband. As our Master and our Husband, He is our Lord; He is our Adonai.
In the New Testament, the main divine titles used are God, Father, Lord, Jesus, Christ, and Holy Spirit.
God in Greek is Theos. God, Theos, equals God, Elohim, in the Old Testament, denoting the unique yet triune God (1 Cor. 8:4, 6; 1 Tim. 2:5a)—the Father being God (1 Pet. 1:2-3), the Son being God (Heb. 1:8), and the Holy Spirit being God (Acts 5:3-4). Theologians have accurately pointed out that the Father, Son, and Spirit are not three separate gods, but three hypostases, or supporting substances, of the one God. Later, theologians began to use the word persons for the three of the Godhead. Person comes from the Latin word persona, which was an actor's mask. One person can have three masks or appearances.
Since I came to the United States, I have spoken much on the Divine Trinity. Some have said wrongly that the three of the Godhead, the Father, Son, and Spirit, are separate from one another. I published something pointing out that the three of the Godhead are distinct but not separate. They are always one. When we have the Father, we have the Son and the Spirit because the three are one. When the Son is here, the Spirit and the Father are with Him. The three are not separate. They are distinct, but one.
God is three yet one. In essence God is one. In economy, in God's move, God is three. This is why the best theology refers to the essential Trinity and the economical Trinity. Essentially God is one, but economically God is three. God the Father sent the Son in His economy, in His move. The Son did things by the Spirit in His move. The Father, Son, and Spirit are three economically in Their move and administration, but not in Their essence. Essentially God is one. This is why the Bible shows that the Son is the Father (Isa. 9:6; John 14:9). Furthermore, Paul said that the last Adam, who was the Son in the flesh, after His death and resurrection became a life-giving Spirit. He said in 2 Corinthians 3:17 that the Lord, the Son, is the Spirit. In verse 18 Paul said that we are being transformed "from the Lord Spirit." The Lord Spirit is a compound title like the Father God and the Lord Christ. This means that the Spirit is the Lord and the Lord is the Spirit.
John indicates that the Son is the expression of the Father. This is why the Son said, "He who has seen Me has seen the Father" (14:9). He also said, "Believe Me that I am in the Father and the Father is in Me" (v. 11). Humanly speaking, no one can understand this. We may say that we are one with another person, but no human being can say that he is in another one and that this other one is in him. The Son is in the Father, and the Father is in the Son. This is coinherence. The three of the Godhead not only coexist but also coinhere. The Son also pointed out that He did not speak from Himself and that His speaking was the Father's speaking and working (vv. 10, 24). This is because the Son and the Father are one. Some may say that they believe that God is triune, when they actually have a tritheistic concept of three gods. The Father, Son, and Spirit are not three gods. They are one God with three aspects—the aspect as the Father, the aspect as the Son, and the aspect as the Spirit.