Catholic Church

The Greek Byzantine Catholic Church (Greek: Ελληνόρρυθμη Καθολική Εκκλησία, Ellinórrythmi Katholikí Ekklisía) or the Greek-Catholic Church of Greece is a sui iuris Eastern Catholic particular church of the Catholic Church that uses the Byzantine Rite in Koine Greek and Modern Greek. Its membership includes inhabitants of Greece and Turkey, with some links with Italy and Corsica.

The Melkite Greek Catholic Church (كنيسة الروم الملكيين الكاثوليك, Kanīsat ar-Rūm al-Malakiyyīn al-Kāṯūlīk; Μελχιτική Ελληνική Καθολική Εκκλησία; Ecclesia Graeca Melchitarum Catholica), also known as the Melkite Byzantine Catholic Church, is an Eastern Catholic church in full communion with the Holy See as part of the worldwide Catholic Church. Its chief hierarch is Patriarch Youssef Absi, whose see is the Cathedral of Our Lady of the Dormition in Damascus, Syria.

The Melkite Church follows the Byzantine Rite and traces its origins to the early Christian community of the Patriarchate of Antioch in the 1st century AD, traditionally founded by the apostle Saint Peter.

Chalcedonian Christianity is the branch of Christianity that accepts and upholds theological resolutions of the Council of Chalcedon, the fourth ecumenical council, held in AD 451. Chalcedonian Christianity accepts the Christological Definition of Chalcedon, a Christian doctrine concerning the union of two natures (divine and human) in one hypostasis of Jesus Christ, who is thus acknowledged as a single person (prosopon). Chalcedonian Christianity also accepts the Chalcedonian confirmation of the Niceno-Constantinopolitan Creed, thus acknowledging the commitment of Chalcedonism to Nicene Christianity.

Chalcedonian Christology is upheld by Roman Catholicism, Eastern Orthodoxy, Lutheranism, Anglicanism and Calvinism (Reformed Christianity), thus comprising the overwhelming majority of Christianity.

A canonical territory is, in some Christian denominations, a geographical area seen as belonging to a particular bishop or Church as its own when it comes to ecclesiastical matters, whether by tradition or by canon law. The concept is found both in the Eastern Orthodox Church and Catholic Church.

According to Andriy Mykhaleyko, the expression "canonical territory" is "rather difficult to define as it can refer to a variety of different aspects, from an ecclesiological, geographical, and cultural entity to the territorial or canonical jurisdiction of a church as an expression of its local community, or the pastoral theological care of the faithful in a particular territory."

In ecclesiology, the Christian Church is what different Christian denominations conceive of as being the true body of Christians or the original institution established by Jesus Christ. "Christian Church" has also been used in academia as a synonym for Christianity, despite the fact that it is composed of multiple churches or denominations, many of which hold a doctrinal claim of being the one true church to the exclusion of the others.

For many Protestant Christians, the Christian Church has two components: the church visible, institutions in which "the Word of God purely preached and listened to, and the sacraments administered according to Christ's institution", as well as the church invisible—all "who are truly saved" (with these beings members of the visible church). In this understanding of the invisible church, "Christian Church" (or catholic Church) does not refer to a particular Christian denomination, but includes all individuals who have been saved. This is in contrast to the one true church applied to a specific concrete Christian institution, a Christian ecclesiological position maintained by the Catholic Church, the Lutheran Churches, the Eastern Orthodox Church, the Oriental Orthodox churches, Assyrian Church of the East, and the Ancient Church of the East. While holding this view, the Lutheran Churches teach that "there are indeed true Christians in other churches" as "other denominations also preach the Word of God, though mixed with error". The branch theory, which is maintained by some Anglicans, holds that those Churches that have preserved apostolic succession are part of the true Church, though the majority of Anglicanism has historically "followed the major continental Reformers in their doctrine of the true church, identifiable by the authentic ministry of word and sacrament, in their rejection of the jurisdiction of the pope, and in their alliance with the civil authority ('the magistrate')".

The Anglican Communion (AC) is a Christian communion consisting of the autocephalous national and regional churches historically in full communion with the archbishop of Canterbury in England, who has acted as a focus of unity, recognised as primus inter pares ("first among equals"), but without formal authority in Anglican provinces outside of the Church of England. Most, but not all, member churches of the communion are the historic national or regional Anglican churches.

With approximately 85–110 million members in 2025, among its 47 member churches, it is the third or fourth largest Christian communion of churches globally, after the Catholic, Eastern Orthodox, and, possibly, World Communion of Reformed Churches. The Anglican Communion considers baptism to be "the traditional gauge" or definition for membership.

A church service (or a worship service) is a formalized period of Christian communal worship, often held in a church building. Most Christian denominations hold church services on the Lord's Day (offering Sunday morning and Sunday evening services); a number of traditions have mid-week services, while some traditions worship on a Saturday. In some Christian denominations, church services are held daily, with these including those in which the seven canonical hours are prayed, as well as the offering of the Mass, among other forms of worship. In addition to this, many Christians attend services on holy days such as Christmas, Ash Wednesday, Good Friday, Ascension Thursday, among others depending on the Christian denomination.

The church service is the gathering together of Christians to be taught the "Word of God" (the Christian Bible) and encouraged in their faith. Technically, the church in "church service" refers to the gathering of the faithful rather than to the physical place in which it takes place. In most Christian traditions services are presided over by clergy wherever possible, but some traditions utilize lay preachers. Styles of service vary greatly, from the Catholic, Lutheran, Eastern Orthodox, Oriental Orthodox, Reformed (Continental Reformed, Presbyterian and Congregationalist) and Anglican traditions of liturgical worship to informal worship characterized by certain free church traditions, common among Methodists and Baptists, that often combine worship with teaching for the believers, which may also have an evangelistic component appealing to backsliders and the non-Christians in the congregation (cf. altar call). Quakers and some other groups have no formal outline to their services, but allow the worship to develop as the participants present feel moved.

Ecclesiastical Latin, also called Church Latin or Liturgical Latin, is a form of Latin developed to discuss Christian thought in late antiquity and used in Christian liturgy, theology, and church administration to the present day, especially in the Catholic Church. It includes words from Vulgar Latin and Classical Latin (as well as Greek and Hebrew) re-purposed with Christian meaning. It is less stylized and rigid in form than Classical Latin, sharing vocabulary, forms, and syntax, while at the same time incorporating informal elements which had always been with the language but which were excluded by the literary authors of Classical Latin.

Its pronunciation was partly standardized in the late 8th century during the Carolingian Renaissance as part of Charlemagne's educational reforms, and this new letter-by-letter pronunciation, used in France and England, was adopted in Iberia and Italy a couple of centuries afterwards. As time passed, pronunciation diverged depending on the local vernacular language, giving rise to even highly divergent forms such as the traditional English pronunciation of Latin, which has now been largely abandoned for reading Latin texts. Within the Catholic Church and in certain Protestant churches, such as the Anglican Church, a pronunciation based on modern Italian phonology, known as Italianate Latin, has become common since the late 19th century.

Mother church or matrice is a term depicting the Christian Church as a mother in her functions of nourishing and protecting the believer. It may also refer to the primary church of a Christian denomination or diocese, i.e. a cathedral church, or the oldest church of a particular locality. For a particular individual, one's mother church is the church in which one received the sacrament of baptism. The term has specific meanings within different Christian traditions. Catholics refer to the Catholic Church as "Holy Mother Church".

Eastern Orthodoxy, otherwise known as Eastern Orthodox Christianity or Byzantine Christianity, is one of the three main branches of Chalcedonian Christianity, alongside Catholicism and Protestantism. Like the Pentarchy of the first millennium, the mainstream (or "canonical") Eastern Orthodox Church is organised into autocephalous churches independent from each other. In the 21st century, the number of mainstream autocephalous churches is seventeen; there also exist autocephalous churches unrecognized by those mainstream ones. Autocephalous churches choose their own primate. Autocephalous churches can have jurisdiction (authority) over other churches, some of which have the status of "autonomous" which means they have more autonomy than simple eparchies.

Many of these jurisdictions correspond to the territories of one or more modern states; the Patriarchate of Moscow, for example, corresponds to Russia and some of the other post-Soviet states. They can also include metropolises, bishoprics, parishes, monasteries, or outlying metochia corresponding to diasporas that can also be located outside the country where the primate resides (e.g., the case of the Ecumenical Patriarchate of Constantinople whose canonical territory is located partly in northern Greece and the east); sometimes they overlap (the case of Moldova where the jurisdictions of the patriarchs of Bucharest and of Moscow overlap).