A denomination, in the Christian sense of the word, is an identifiable religious body under a common name, structure, and/or doctrine. Christianity is composed of four major divisions of Churches: Roman Catholic, Eastern Orthodox, Oriental Orthodox and Protestant.

Each of these four divisions has important subdivisions. Because the Protestant subdivisions do not maintain a common theology or earthly leadership, they are far more distinct than the subdivisions of the other three groupings.

Denomination typically refers to one of the many Christian groupings including each of the multitude of Protestant subdivisions. Denominationalism is an ideology which views some or all Christian groups as being, in some sense, versions of the same thing regardless of their distinguishing labels. Not all churches teach this. The Roman Catholic and Orthodox Churches do not use this term as its implication of interchangeability does not agree with their theological teachings. There are some groups which practically all others would view as apostate or heretical, and not legitimate versions of Christianity.

There were some movements considered heresies by the early church which do not exist today and are not generally referred to as denominations. Examples include the Gnostics (who had believed in an esoteric dualism), the Ebionites (who venerated Christ's blood relatives), and the Arians. The greatest divisions in Christianity today, however, are between Eastern Orthodoxy, Roman Catholicism, and various denominations formed during and after the Protestant Reformation. There also exists in Protestantism and Orthodoxy various degrees of unity and division.

Comparisons between denominational churches must be approached with caution. For example, in some churches, congregations are part of a larger church organization, while in other groups, each congregation is an independent autonomous organization. This issue is further complicated by the existence of groups of congregations with a common heritage that are officially nondenominational and have no centralized authority or records, but which are identified as denominations by non-adherents. Study of such churches in denominational terms is therefore a more complex proposition.

Numerical comparisons are also problematic. Some groups count membership based on adult believers and baptized children of believers, while others only count adult baptized believers. Others may count membership based on those adult believers who have formally affiliated themselves with the congregation. In addition, there may be political motives of advocates or opponents of a particular group to inflate or deflate membership numbers through propaganda or outright deception.

Historical schisms and methods of classification scheme
Christianity has not been a monolithic faith since the first century, if ever, and today there exist a large variety of groups that share a common history and tradition within and without mainstream Christianity. Since Christianity is the largest religion in the world (making approximately one-third of the population), it is necessary to understand the various faith traditions in terms of commonalities and differences between tradition, theology, church government, doctrine, language, and so on.

The largest division in many classification schemes is between the families of Eastern and Western Christianity. After these two larger families come distinct branches of Christianity. Most classification schemes list six (in order of size: Roman Catholicism, Protestantism, Eastern Orthodoxy, Anglicanism, Oriental Orthodoxy, and Assyrians). Others may include Restorationism as a seventh, but classically this is included among Protestant movements. Some include Anabaptism as an eighth, although Anabaptism is often, incorrectly, included among Protestant movements. After these branches come denominational families. In some traditions, these families are precisely defined (such as the autocephalous churches in both Orthodox branches), in others, they may be loose ideological groups with overlap. This is especially the case in Protestantism, which includes Adventists, Anabaptists, Baptists, Congregationalists, Lutherans, Methodists, Pentecostals, Presbyterians, Reformed churches, and possibly others, depending on who is organizing the scheme. Anglicans are often grouped with Protestants, but also may be considered separately. From there come denominations, which in the West, have complete independence to establish doctrine (for instance, national churches in the Anglican Communion or in Lutheranism). At this point, the scheme becomes more difficult to apply to the Eastern churches and Roman Catholic faiths, due to their hierarchical structures. More precise units after denominations include kinds of regional councils and individual congregations and church bodies.

A schematic of Christian denominational taxonomy.
The initial differences between the East and West traditions stem to socio-cultural and linguistic divisions in and between the Western Roman and Byzantine Empires. Since the West (that is, Western Europe) spoke Latin as its lingua franca and the East (Eastern Europe, the Middle East, Asia, and northern Africa) largely used Koine Greek to transmit writings, theological developments were difficult to translate from one branch to the other. In the course of ecumenical councils (large gatherings of Christian leaders), some church bodies split from the larger family of Christianity. Many earlier heretical groups either died off for lack of followers and/or suppression by the church at large (such as Apollinarians, Montanists, and Ebionites).

The first significant, lasting split in historic Christianity came from the Assyrian Church of the East, who left following the Christological controversy over Nestorianism in 431 (the Assyrians in 1994 released a common Christological statement with the Roman Catholic church). Today, the Assyrian and Roman Catholic churches view this schism as largely linguistic, due to problems of translating very delicate and precise terminology from Latin to Aramaic and vice-versa (see Council of Ephesus). Following the Council of Chalcedon in 451, the next large split came with the Syrian and Alexandrian (Egyptian or Coptic) churches dividing themselves, with the dissenting churches becoming today's Oriental Orthodoxy. (A similar Christological statement was made between Pope John Paul II and Syriac patriarch Ignatius Zakka I Iwas, as well as between representatives of both Eastern and Oriental Orthodoxy).

Although the church as a whole didn't experience any major divisions for centuries afterward, the Eastern and Western groups drifted until the point where patriarchs from both families excommunicated one another in about 1054 in what is known as the Great Schism. The political and theological reasons for the schism are complex, but one major controversy was the inclusion and acceptance in the West of the filioque clause into the Nicene Creed, which the East viewed as erroneous. Another was the definition of papal primacy. Both West and East agreed that the patriarch of Rome (ie. the Pope) was owed a "primacy of honour" by the other patriarchs (those of Alexandria, Antioch, Constantinople and Jerusalem), but the West also contended that this primacy extended to jurisdiction, a position rejected by the Eastern patriarchs. Various attempts at dialogue between the two groups would occur, but it was only in the 1960s, under Pope Paul VI and Patriarch Athenagoras, that significant steps began to be made to mend the relationship between the two.

In Western Christianity, there were a handful of geographically-isolated movements that preceded the spirit of the Protestant Reformation. The Cathars were a very strong movement in medieval southwestern France, but did not survive into modern times. In northern Italy and southeastern France, Peter Waldo founded the Waldensians in the 12th century. This movement has largely been absorbed by modern-day Protestant groups. In Bohemia, an Orthodox region, the Papal States (then a much more powerful land empire than today's Holy See) took over the region and converted it to the Roman Catholic faith. A movement in the early 15th century by Jan Hus called the Hussites defied Roman Catholic dogma and still exists to this day (alternately known as the Moravians).

A huge schism was unintentionally founded by the posting of Martin Luther's 95 Theses in Saxony on October 31, 1517. Initially written as a set of grievances to spur the Roman Catholic church into reforming itself, rather than beginning a new sect, Luther's writings combined with the work of Swiss theologian Huldrych Zwingli and French theologian and politician John Calvin instigating a rift in European Christianity that created today's second-largest branch of Christianity after Roman Catholicism itself, Protestantism. In England, Henry VIII of England declared himself to be supreme governor of the Church of England with the Act of Supremacy in 1531, founding the English Reformation, though with much more subdued goals than reformations of Calvin or Ulrich Zwingli.

Unlike the other branches (Roman Catholicism, Eastern and Oriental Orthodoxy, the Assyrians, and Anglicans), Protestantism is a general movement that has no internal governing structure. As such, diverse groups such as Adventists, Anabaptists, Baptists, Congregationalists, Lutherans, Methodists, Presbyterians, Reformed, Pentecostals, and possibly Anglicans and Restorationists (depending on one's classification scheme) are all a part of the same family, and with further doctrinal variations within each group. The largest amount of new churches and denominations have come from Protestantism in its first four hundred years, compared to the millennium and a half prior in all of Christendom.

The Old Catholic Church split from the Roman Catholic Church in the 1870s because of the promulgation of the dogma of Papal Infallibility as promoted by the First Vatican Council of 1869–1870. The term 'Old Catholic' was first used in 1853 to describe the members of the See of Utrecht that were not under Papal authority. The Old Catholic movement grew in America but has not maintained ties with Utrecht, although talks are under way between independent Old Catholic bishops and Utrecht.

Western churches
Roman Catholicism and Protestantism are the two major divisions of Christianity in the Western world, if Anglicanism is included as a part of the latter. However, Catholics do not describe themselves as a denomination but rather as a Church. The Baptist, Methodist, and Lutheran churches are generally considered to be Protestant denominations, although strictly speaking, of these three, the Lutheran denomination, is the only one of these founded as a "protest" against Roman Catholicism. Anglicanism is generally classified as Protestant, but since the "Tractarian" or Oxford Movement of the 19th century, led by John Henry Newman, Anglican writers emphasize a more catholic understanding of the church and characterize it as more properly understood as its own tradition — a via media ("middle way"), both Protestant and Catholic. A case could be made to understand Lutheranism in a similar way considering the catholic character of its foundational documents (the Augsburg Confession and other documents contained in the Book of Concord) and its historic separation from Calvinistic and Reformed Churches, out of which all other Protestant denominations arise in one way or another.

One central tenet of Roman Catholicism is its practice of apostolic succession. "Apostle" means "one who is sent out." Jesus commissioned the first twelve apostles (see Biblical Figures for the list of the Twelve), and they, in turn laid hands on subsequent church leaders to ordain (commission) them for ministry. In this manner, Roman Catholics trace their ordained ministers all the way back to the original Twelve. Roman Catholics are distinct in their belief that the Pope has authority which can be traced directly to the apostle Peter. There are smaller churches, such as the Old Catholic Church which rejected the definition of papal infallibility at the First Vatican Council, and Anglo-Catholics, Anglicans who believe that Anglicanism is a continuation of historical Catholicism and who incorporate many Catholic beliefs and practices. Catholicism (cf. the Roman Catholic Church) is sometimes referred to as Roman Catholicism by those Protestants who also consider themselves a part of the catholic church and by Old Catholics. Those who belong to the Roman Catholic Church do not consider Protestants to be part of the Catholic faith. They also consider the title "Roman" Catholic to be an inaccurate reflection of the make-up of their Catholic faith, as there are other religious rites than the Latin Rite (which makes up the vast majority of believers). These smaller groups are particular Eastern Rite Catholic churches in communion with Rome. Roman Catholicism has a hierarchical structure in which supreme authority for matters of faith and practice are the exclusive domain of the Pope and the bishops when acting in union with him. Most Roman Catholics are unaware of the existence of Old Catholicism.

Since Protestantism does not represent a unified body of believers, but a faith tradition which itself has split many times, it is more often understood in large denominational families. Each Protestant movement has developed freely, and many have split over theological issues. For instance, a number of movements that grew out of spiritual revivals, like Methodism and Pentecostalism. Doctrinal issues and matters of conscience have also divided Protestants. The Anabaptist tradition, made up of the Amish, Hutterites, and Mennonites, rejected the Roman Catholic and Lutheran doctrines of infant baptism; this tradition is also noted for its belief in pacifism. Many churches in the Restorationist group reject being identified as Protestant or even as denominations, as they use only the Bible not creeds of men, and model the church after the first century church found in scripture; the churches of Christ is one example, African Initiated Churches, like Kimbanguism, mostly fall within Protestantism, with a varying degree of syncretism. The measure of mutual acceptance between the denominations and movements varies, but is growing largely due to the ecumenical movement in the 20th century and overarching Christian bodies such as the World Council of Churches. Protestant theology for each denomination is usually guarded by local church councils.

Eastern churches
In the Eastern world, the largest body of believers is the Eastern Orthodox Church, sometimes erroneously called "Greek Orthodox." The Eastern Orthodox Church also believes it is the continuation of the original Christian church established by Jesus. According to the Eastern Churches' understanding of Papal primacy, the bishop of Rome was first in honor among the bishops, but possessed no direct authority over dioceses other than his own and no influence over other dioceses than those which naturally fall under his patriarchal jurisdiction. Consequently, each church in the Eastern Orthodoxy is autocephalous, and is internally responsible for matters of doctrine and practice. Today, the Patriarch of Constantinople (modern-day Istanbul, Turkey) is known as the Ecumenical Patriarch, and holds the title of honor among other bishops (see primus inter pares, or first among equals). In addition to the four ancient churches there are approximately 10 others organized more or less along national lines (there is some controversy over whether or not the Orthodox Church in America is or should be autocephalous). The largest of these, and the largest Eastern Orthodox Church overall, is the Russian Orthodox Church. Many of these groups are represented as independent ecclesiastical bodies in America who, for the most part, are still in full Communion with each other. In addition, smaller Orthodox communities have a large degree of internal responsibility, known as autonomy, but are under the authority of another regional church. Small schisms exist today with "Old calendarists" groups and national churches that are not in communion with other Eastern Orthodox Churches (such as the Macedonian Orthodox Church and Montenegrin Orthodox Church).

The Oriental Orthodox organizes its church in a similar manner, with six national autocephalous groups and two autonomous bodies. Although the region of modern-day Ethiopia and Eritrea has had a strong body of believers since the infancy of Christianity, these regions only gained autocephaly in 1963 and 1994 respectively. Since these groups are relatively obscure in the West, literature on them has sometimes included the Assyrian Church of the East as a part of the Oriental Orthodox Communion, but the Assyrians have maintained theological, cultural, and ecclesiastical independence from all other Christian bodies since 431. The church is administered in a hierarchical model not entirely unlike the Catholics, with the head of the church being the Patriarch Catholicos of Babylon, currently HH Mar Dinkha IV. Due to oppression, the church's headquarters is in Chicago, Illinois, rather than Assyria (Syria, northern Iraq and part of Iran). Some believers have remained in the Middle East, though, and a small congregation still exists due to missionary efforts of the 7th and 8th centuries in China. Even within this small group, there is a rival Catholicos (Patriarch) in California.

Christianity outside of the mainstream
While a precise definition of what constitutes mainstream Christianity is difficult at best, there are some groups that fall outside of what is popularly construed to be Christian groups, but share some manner of historical connection with the larger community of Christians.

Considering this diversity, it may be impossible to define what Christianity is without either rejecting all definitions, or adopting a particular definition as authoritative and thus excluding others. In terms of the modern aim of scientific and objective definition, both options are considered problematic.

Christianity, even in its infancy as a Jewish sect, rejected ethnic definition. It was conceived and grew as an international religion with global ambitions, spreading rapidly from Judea to nations and people all over the world. Doctrines, rather than ethnicity, define essential Christianity - even where ethnic groups have been Christian for generations. The multiplicity of communities of faith may be partly accounted for by the definition of Christianity according to specific points of indispensable doctrine, the denial of which sets the heretic, or apostate, outside of the "Church", where perhaps he is accepted by another "Church" holding doctrines compatible with his own.

Points of distinctive doctrine may be a very small number of simple propositions, or very numerous and difficult to explain, depending on the group. Some groups are defined relatively statically, and others have changed their definitions dramatically over time. As an example, before the Enlightenment, Christian teachers who denied the doctrine of the Holy Trinity (a widely held doctrine about the nature of God the Father, Jesus the Son, and the Holy Spirit formulated from the intrepretation of New Testament passages in 325), would be cast out of their churches, and at times exiled or otherwise deprived of the protection of law. In later times, some points of the traditional doctrine of the Trinity are considered false doctrines according to groups such as The Church of Jesus Christ of Latter-day Saints, the Iglesia ni Cristo, Christadelphians, and the Jehovah's Witnesses (representing tens of millions of believers combined). For example, Latter-day Saints teach that God the Father, His Son Jesus Christ, and the Holy Ghost are three distinct beings. Some groups, like Community of Christ, have their roots in the Restoration Movement and the Latter Day Saint Movement but have reformed to such an extent that they are now trinitarian and striving to be recognized as mainstream Christianity.

Other movements coalesced to form today's Unitarian Universalism, whose member congregations recognize to varying degrees and in different ways their Christian origins. Unitarians and Universalists have historically been non-creedal and congregations have been self-governing, such that when the denominations consolidated in 1961, some congregations and individual Unitarian Universalists continued to identify themselves broadly as Christian, even more as "followers of Jesus."

Another group, the local churches, is similar in many respects to mainstream Christianity but theologically reject denominationalism altogether.

Christians with Jewish roots
One group which has maintained its Jewish identity alongside an acceptance of Jesus as the Messiah and the New Testament as authoritative are Messianic Jews, also called Hebrew Christians. Since the founding of the church, there have been Jewish elements retained by particular groups that wanted to retain their national heritage alongside the Gospel message. In fact, the first council was called in Jerusalem to address just this issue, and the deciding opinion was written by Christ's brother James the Just, the first bishop of Jerusalem and a pivotal figure in the Christian movement. One of the best known groups of Messianic Jews in the United States today is Jews for Jesus, and due to the entirely different history of such movements and groups, they defy any simple classification scheme.

Uncategorized
Some denominations which arose alongside the Western Christian tradition consider themselves Christian, but neither Roman Catholic nor wholly Protestant, such as the Religious Society of Friends (Quakers). Quakerism began as a mystical and evangelical Christian movement in 17th century England, eschewing priests and all formal Anglican or Roman Catholic sacraments in their worship, including many of those practices that remained among the stridently Protestant Puritans such as baptism with water. Like the Mennonites, Quakers traditionally refrain from participation in war. The Salvation Army is often, albeit incorrectly, understood to be a social relief organization. It is, in fact, a denomination which does extensive social relief work.

Messianic movements
Other faith traditions claim not to be descended from any of these groups directly. The Church of Jesus Christ of Latter-day Saints, for instance, is often grouped with the Protestant churches, but does not characterize itself as Protestant. Its origination during the Second Great Awakening parallels the founding of numerous other indigenous American religions, especially in the Burned-over district of western New York state, and in the western territories of the United States, including the Adventist movement, the Jehovah's Witnesses, Christian Science (which had roots in Congregationalism but regarded itself as restorative), and the Restoration Movement (sometimes called "Campbellites" or "Stone-Campbell churches", which include the Christian Church (Disciples of Christ) and the Church of Christ). Each of these groups, founded within fifty years of one another, originally claimed to be an unprecedented, late restoration of the primitive Christian church.

New Thought
Another family of Christian churches are grouped together under the banner of "New Thought" churches. Although the terminology is inaccurate, these churches share a metaphysical or mystical predisposition and understanding of the Bible. The concept was founded by Emma Curtis Hopkins after breaking off from Mary Baker Eddy's Church of Christ, Scientist. One of the oldest metaphysical Christian groups are the Swedenborgians, founded on the teachings of Emanuel Swedenborg in 1787. The latter part of the 19th century also saw the founding of Spiritism by Allan Kardec and the Unity Church by Charles Fillmore and Myrtle Fillmore. Lastly, the mystical elements of Yoruba mythology, an African animistic tradition combined with Roman Catholicism via Afro-Cuban slaves, forming Lukumí (more well-known in America by its branch Santeria).

Mandaeans
One peculiar body presents virtually the last Gnostic group in existence. The Mandaeans were discovered in obscurity on the coast of modern-day Iraq and Iran by Portuguese missionaries in the 14th century. They were erroneously identified as "Christians of John the Baptist", but reject Jesus Christ entirely as a false prophet, and following esoteric teachings they claim come from John the Baptist himself. Another small Gnostic group which purports itself to be a "Buddhist branch of original Christianity" are the Essenes. These syncretists are entirely unrelated to the ancient Jewish sect of the same name.

The Christian Community
The Christian Community (German: Die Christengemeinschaft) is a worldwide Movement for Religious Renewal. It was founded in 1922 in Switzerland by the Lutheran theologian and minister Friedrich Rittlemeyer, inspired by Rudolf Steiner, the Austrian mystic and founder of Anthroposophy. Both Protestants and Roman Catholics took part in the initial development of this movement, which combines a "high church" regard for the spiritual significance of the mass with rational theology and freedom of thought.

Christian-related movements
Two movements which are entirely unrelated in their founding share a common element of an additional Messiah or incarnation of Christ: the Unification Church and the Rastafari movement. These groups would also fall outside of traditional taxonomies of Christian groups.

There are also some Christians that reject organized religion altogether. Christian anarchists believe that the original teachings of Jesus were corrupted first by Saint Paul and then by Roman statism (see early Christianity), and that earthly authority such as government, or indeed the established Church, do not and should not have power over them. Following "The Golden Rule", they oppose the use of physical force in any circumstance, and advocate nonviolence. Russian Count and author Leo Tolstoy, widely regarded as one of the greatest novelists of all time for his masterpieces War and Peace and Anna Karenina, who also wrote The Kingdom of God Is Within You, [1] was a Christian anarchist.

Related independent religions
In addition, Christianity has partly inspired other religions, like the Bahá'í Faith, whose adherents do not consider themselves Christians but do consider Jesus to be a prophet and the Messiah (Anointed one) promised in the Old Testament, and, in the case of the Bahá'ís, the Son of God.

Christian mystery movements
Main articles: Esoteric Christianity and The Rosicrucian Fellowship
The religion of the Christ is taught as a mystery religion. It's composed of schools, currents or movements which have an occult system of thought based on esoteric knowledge. They aim aid to prepare the individual toward spiritual evolution. It almost always deal with some system of esoteric cosmology and contain some common themes as rebirth, occult history of human evolution, planes of existence, and Initiation into those same planes or inner worlds.