Historically, many rulers have assumed titles such as son of God, son of a god or son of heaven.
The term "son of God" is sometimes used in the Old and New Testaments of the Christian Bible to refer to those with special relationships with God. In the Old Testament, angels, just and pious men, the descendants of Seth, and the kings of Israel are all called "sons of God." In the New Testament, Adam, and, most notably, Jesus Christ are called "son of God," while followers of Jesus are called, "sons of God."
In the New Testament, "Son of God" is applied to Jesus on many occasions. Jesus is declared to be the Son of God on two separate occasions by a voice speaking from Heaven. Jesus is also explicitly and implicitly described as the Son of God by himself and by various individuals who appear in the New Testament. As applied to Jesus, the term is a reference to his role as the Messiah, the King chosen by God. The contexts and ways in which Jesus' title, Son of God, means something more than or other than Messiah remain the subject of ongoing scholarly study and discussion.
The term "Son of God" should not be confused with the term "God the Son" (Greek: Θεός ὁ υἱός), the second Person of the Trinity in Christian theology. The doctrine of the Trinity identifies Jesus as God the Son, identical in essence but distinct in person with regard to God the Father and God the Holy Spirit (the first and third Persons of the Trinity). Nontrinitarian Christians accept the application to Jesus of the term "Son of God", which is found in the New Testament, but not the term "God the Son", which is not found there.