The word "Christian" is derived from the name "Christ," Greek for "the annointed one." He is quite often spoken of as "Jesus Christ," or Jesus the Christ." Jewish tradition had long taught that God would one day send a Savior, called a Messiah, to save his people. To Christians, Jesus was that Messiah, and fulfilled the prophecies of the Old Testament. He is believed by Christians to be the son of God, and a member of the Trinity which comprises the Christian God. In early Christianity, there was tremendous debate about his exact nature, whether God or Man. The Council of Nicea decided that Jesus was both God and Man. As the son of God, he also was the perfect sacrifice demanded for the sins of the world. According to Christian tradition, his crucifixion was in fact a sacrifice for sin. He was believed to be without sin, therefore he was the perfect sacrifice.