Christianity (from the Ancient Greek word Χριστός, Khristos, "Christ", literally "anointed one") is a monotheistic religion based on the life and teachings of Jesus of Nazareth as presented in canonical gospels and other the New Testament writings. Adherents of the Christian faith are known as Christians. Mainstream Christianity teaches Jesus is the Son of God, God having become human and the savior of humanity. Because of this, Christians commonly refer to Jesus as Christ or Messiah. The three largest groups in the world of Christianity are the Roman Catholic Church, the Eastern Orthodox Church, and the various churches of Protestantism. The Roman Catholic and Eastern Orthodox patriarchates split from one another in the East-West Schism of 1054 AD, and Protestantism came into existence during the Protestant Reformation of the 16th century, splitting from the Roman Catholic Church.
Christianity began as a Jewish sect in the mid-1st century. Originating in the eastern Mediterranean, it 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, Ethiopia and parts of India. Following the Age of Discovery, through missionary work and colonization, Christianity spread to the Americas, Australasia, and the rest of the world. Christianity, therefore, is a major influence in the shaping of Western civilization.
Christians believe that Jesus is the Messiah prophesied in the Hebrew Bible, referred to as the "Old Testament" in Christianity. The foundation of Christian theology is expressed in the early Christian ecumenical creeds, which contain claims predominantly accepted by followers of the Christian faith.These professions state that Jesus suffered, died, was buried, and was resurrected from the dead to open heaven to those who believe in him and trust him for the remission of their sins (salvation). They further maintain that Jesus bodily ascended into heaven where he rules and reigns with God the Father. Most denominations teach that Jesus will return to judge all humans, living and dead, and grant eternal life 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.
As of the early 21st century, Christianity has around 2.2 billion adherents. Christianity represents about a quarter to a third of the world's population and is the world's largest religion. In addition, Christianity is the state religion of several countries.