Christianity kk (from the Greek word Kristos Xριστός "Christ") is a monotheistic religion centered on the life and teachings of Jesus as presented in the New Testament. Adherents of Christianity, known as Christians, believe that Jesus is the Son of God and the Messiah prophesied in the Hebrew Bible (the part of scripture common to Christianity and Judaism). The majority of orthodox Christian theology claims that Jesus suffered, died, and was resurrected to bring about salvation from sin. They further maintain that Jesus ascended into heaven, and most denominations teach that Jesus will return to judge all humans, living and dead, and grant immortality to his followers. He is considered the model of a virtuous life, and both the revealer and physical incarnation of God. Christians call the message of Jesus Christ the Gospel ("good news") and hence refer to the earliest written accounts of his ministry as gospels. Like Judaism and Islam, Christianity is classified as an Abrahamic religion (see also Judeo-Christian). Christianity began as a Jewish sect in the eastern Mediterranean, quickly grew in size and influence over a few decades, and by the 4th century had become the dominant religion within the Roman Empire. During the Middle Ages, most of the remainder of Europe was Christianized, with Christians also being a (sometimes large) religious minority in the Middle East, North Africa, and parts of India. Following the Age of Discovery, through missionary work and colonization, Christianity spread to the Americas and the rest of the world. Christianity has played a prominent role in the shaping of Western civilization at least since the 4th century. As of the early 21st century, Christianity has between 1.5 billion and 2.1 billion adherents, representing about a quarter to a third of the world's population and is the world's largest religion.