Christianity is a monotheistic religion centered on Jesus of Nazareth and his life, death, resurrection, and teachings as presented in the New Testament. Christians believe Jesus to be the Son of God and the Messiah prophesied in the Old Testament. With an estimated 2.1 billion adherents in 2001, Christianity is the world's largest religion. It is the predominant religion in the Americas, Europe, Philippine Islands, East Timor, Oceania, and large parts of Africa (see Christianity by country). It is also growing rapidly in Asia, particularly in China and South Korea, and in Northern Africa.
Christianity began in the 1st century AD as a Jewish sect, and shares many religious texts with Judaism, specifically the Hebrew Bible, known to Christians as the Old Testament. Like Judaism and Islam, Christianity is classified as an Abrahamic religion. The name "Christian" was first applied to the disciples in Antioch, as recorded in Acts 11:26. The earliest recorded use of the term Christianity is by Ignatius of Antioch.
There is a diversity of doctrines and practices among groups calling themselves Christian. These groups are sometimes classified under denominations, though for theological reasons many groups reject this classification system. Christianity may be broadly represented as being divided into three main groupings.
Roman Catholicism: The Roman Catholic Church, the largest single body, includes the Latin Rite and several Eastern Catholic Rites and totals more than 1 billion baptized members.
Eastern Christianity: Eastern Orthodox Churches, Oriental Orthodox Churches, the 100,000 member Assyrian Church of the East, and others with a combined membership of more than 300 million baptized members
Protestantism: Groups such as Anglicans, Lutherans, Reformed/Presbyterians, Congregational/United Church of Christ, Evangelical, Charismatic, Baptists, Methodists, Nazarenes, Anabaptists, Seventh-day Adventists and Pentecostals. The oldest of these separated from the Roman Catholic Church in the 16th century Protestant Reformation, followed in many cases by further divisions. Estimates of the total number of Protestants are very uncertain, partly because of the difficulty in determining which denominations should be placed in this category, but it seems to be unquestionable that Protestantism is the second major branch of Christianity (after Roman Catholicism) in number of followers.
Some Protestants identify themselves simply as Christian, or born-again Christian; they typically distance themselves from the confessionalism of many Protestant communities by calling themselves "non-denominational" — often founded by individual pastors, they have little affiliation with historic denominations. Others, particularly some Anglicans, eschew the term Protestant and thus insist on being thought of as Catholic, adopting the name "Anglo-Catholic". This view is not shared by the Roman Catholics, mainly because of doctrinal differences. Finally, various small communities, such as the Old Catholic and Independent Catholic Churches, are similar in name to the Roman Catholic Church, but are not in communion with the See of Rome. The Roman Catholic Church was simply called the "Catholic Church" until other groups started considering themselves "Catholic". The term "Roman Catholic" was made to distinguish the Roman Catholics from other groups.
Restorationists, who are historically connected to the Protestant Reformation, do not usually describe themselves as "reforming" a Christian Church continuously existing from the time of Jesus, but as restoring the Church that they believe was lost at some point. Restorationists include Churches of Christ with 2.6 million members, Disciples of Christ with 800,000 members, The Church of Jesus Christ of Latter-day Saints with 12 million members, and Jehovah’s Witnesses with 6.6 million members. Though Restorationists have some basic similarities, their doctrine and practices vary significantly.
Certain of these groups deviate from the tenets which most groups hold as basic to Christianity and are considered heretical or even non-Christian by many mainstream Christian groups; this is particularly true for non-trinitarians.
Most churches have long expressed ideals of being reconciled with each other, and in the 20th Century Christian ecumenism advanced in two ways. One way was greater cooperation between groups, such as the Edinburgh Missionary Conference of Protestants in 1910, the Justice, Peace and Creation Commission of the World Council of Churches founded in 1948 by Protestant and Orthodox churches, and similar national councils like the National Council of Churches in Australia which also includes Roman Catholics.
The other way was institutional union with new United and uniting churches. Congregationalist, Methodist, and Presbyterian churches united in 1925 to form the United Church of Canada and in 1977 to form the Uniting Church in Australia. The Church of South India was formed in 1947 by the union of Anglican, Methodist, Congregationalist, Presbyterian, and Reformed churches.
Steps towards union on a global level have also been taken in 1965 by the Catholic and Orthodox churches mutually revoking the excommunications that marked their Great Schism in 1054; the Anglican Roman Catholic International Commission (ARCIC) working towards full communion between those churches since 1970; and the Lutheran and Catholic churches signing The Joint Declaration on the Doctrine of Justification in 1999 to address conflicts at the root of the Protestant Reformation. In 2006 the Methodist church also adopted the declaration,
Christians identify Jesus as God incarnate and the Messiah. The title Messiah comes from the Hebrew word מָשִׁיחַ (māšiáħ) meaning "the anointed one". The Greek translation Χριστός (Christos) is the source of the English word Christ. Christians believe that, as Messiah, Jesus was anointed as ruler and savior of both the Jewish people specifically and of humanity in general, and hold that Jesus coming was the fulfillment of messianic prophecies of the Old Testament. The Christian concept of Messiah differs significantly from the contemporary Jewish concept.
Most Christians believe that Jesus is "true God and true man" (or both fully divine and fully human). Jesus, having become fully human in all respects, including the aspect of mortality, suffered the pains and temptations of mortal man, yet he did not sin. As fully God, he defeated death and rose to life again with the resurrection. According to Christian Scripture, while still a virgin, Mary conceived Jesus not by sexual intercourse, but by the power of the Holy Spirit.
Little of Jesus childhood is recorded in the Gospels compared to his adulthood, especially the week before his death. The Biblical accounts begin with his baptism, and go on to recount miracles (e.g. turning water into wine at a marriage at Cana, exorcisms, healings, &c.), quote his teachings (e.g. the Sermon on the Mount and parables) and narrate his deeds (e.g. calling the Twelve Apostles and sharing hospitality with outcasts and the poor).