Eucharist

Christian liturgy is a pattern for worship used (whether recommended or prescribed) by a Christian congregation or denomination on a regular basis. The term liturgy comes from Greek and means "public work". Within Christianity, liturgies descending from the same region, denomination, or culture are described as ritual families.

When Christians meet for worship, they perform a liturgy (work), offering service to God together. The majority of Christian denominations hold their principal church service on Sunday, the first day of the week, which is known as the Lord's Day. In some Christian denominations, liturgies are held daily, with these including those in which the canonical hours are prayed, as well as the offering of the Eucharistic liturgies such as Mass, among other forms of worship. In addition to this, many Christians attend services of worship on holy days such as Christmas, Ash Wednesday, Good Friday, Ascension Thursday, among others depending on the Christian denomination.

An accident (Greek συμβεβηκός), in metaphysics and philosophy, is a property that the entity or substance has contingently, without which the substance can still retain its identity. An accident does not affect its essence, according to many philosophers. It does not mean an "accident" as used in common speech, a chance incident, normally harmful. Examples of accidents are color, taste, movement, and stagnation. Accident is contrasted with essence: a designation for the property or set of properties that make an entity or substance what it fundamentally is, and which it has by necessity, and without which it loses its identity.

Aristotle made a distinction between the essential and accidental properties of a thing. Thomas Aquinas and other Catholic theologians have employed the Aristotelian concepts of substance and accident in articulating the theology of the Eucharist, particularly the transubstantiation of bread and wine into body and blood.

Reformed Christianity, also called Calvinism, is a major branch of Protestantism that began during the 16th-century Protestant Reformation. In the modern day, it is largely represented by the Continental Reformed, Presbyterian, and Congregational traditions, as well as parts of the Anglican (known as "Episcopal" in some regions), Baptist and Waldensian traditions, in addition to a minority of persons belonging to the Methodist faith (who are known as Calvinistic Methodists).

Reformed theology emphasizes the authority of the Bible and the sovereignty of God, as well as covenant theology, a framework for understanding the Bible based on God's covenants with people. Reformed churches emphasize simplicity in worship. Several forms of ecclesiastical polity are exercised by Reformed churches, including presbyterian, congregational, and some episcopal. Articulated by John Calvin, the Reformed faith holds to a spiritual (pneumatic) presence of Christ in the Lord's Supper.

The East–West Schism, also known as the Great Schism or the Schism of 1054, is the break of communion between the Catholic Church and the Eastern Orthodox Church since 1054. A series of ecclesiastical differences, theological disputes and geopolitical tensions between the Greek East and Latin West preceded the formal split that occurred in 1054. Prominent among these were the procession of the Holy Spirit (Filioque), whether leavened or unleavened bread should be used in the Eucharist, iconoclasm, the coronation of Charlemagne as emperor of the Romans in 800, the pope's claim to universal jurisdiction, and the place of the See of Constantinople in relation to the pentarchy.

The first action that led to a formal schism occurred in 1053 when Patriarch Michael I Cerularius of Constantinople ordered the closure of all Latin churches in Constantinople. In 1054, the papal legate sent by Leo IX travelled to Constantinople in order, among other things, to deny Cerularius the title of "ecumenical patriarch" and insist that he recognize the pope's claim to be the head of all of the churches. The main purposes of the papal legation were to seek help from the Byzantine emperor, Constantine IX Monomachos, in view of the Norman conquest of southern Italy, and to respond to Leo of Ohrid's attacks on the use of unleavened bread and other Western customs, attacks that had the support of Cerularius. The historian Axel Bayer says that the legation was sent in response to two letters, one from the emperor seeking help to organize a joint military campaign by the eastern and western empires against the Normans, and the other from Cerularius. When the leader of the legation, Cardinal Humbert of Silva Candida, O.S.B., learned that Cerularius had refused to accept the demand, he excommunicated him, and in response Cerularius excommunicated Humbert and the other legates. According to Kallistos Ware, "Even after 1054 friendly relations between East and West continued. The two parts of Christendom were not yet conscious of a great gulf of separation between them ... The dispute remained something of which ordinary Christians in East and West were largely unaware".

The New Covenant (Ancient Greek: διαθήκη καινή, romanized: diathḗkē kainḗ) is a biblical interpretation which was originally derived from a phrase in the Book of Jeremiah (Jeremiah 31:31–34), in the Hebrew Bible (or the Old Testament of the Christian Bible). Generally, Christians believe that the promised New Covenant—new relationship with God—was instituted at the Last Supper as part of the Eucharist, which, in the Gospel of John, includes the New Commandment.

Most Christians believe that Jesus is the mediator of the New Covenant, and they also believe that the blood of Christ, which was shed during his crucifixion, is the only blood sacrifice which is required by the covenant. Based on the biblical passage in the Epistle to the Hebrews (9:16–17) which reads that, "Where a will is involved, the death of the one who made it must be established. For a will takes effect only at death, since it is not in force as long as the one who made it is alive." Protestants tend to believe that the New Covenant came into force with the death of Jesus the Christ, and the commentary to the Roman Catholic New American Bible also says that Christ is the "testator whose death puts his will into effect".

An ordinance is a term used by certain Christian denominations for a religious ritual that was instituted by Jesus for Christians to observe.

Examples of ordinances include baptism and the Lord's Supper, both of which are practiced in denominations including the Anabaptist, Baptist, Churches of Christ, and Pentecostal denominations. Some churches, including those of the Anabaptists, include headcovering and footwashing as ordinances.

Liturgy is the customary public ritual of worship performed by a religious group. As a religious phenomenon, liturgy represents a communal response to and participation in the sacred through activities reflecting praise, thanksgiving, remembrance, supplication, or repentance. It forms a basis for establishing a relationship with God or the divine.

Technically speaking, liturgy forms a subset of ritual. The word liturgy, sometimes equated in English as "service", refers to a formal ritual enacted by those who understand themselves to be participating in an action with the divine.

The Armenian Rite (Armenian: Հայկական պատարագ) is a liturgical rite used by both the Armenian Apostolic and the Armenian Catholic churches. Isaac of Armenia, the Catholicos of All Armenians, initiated a series of reforms with help from Mesrop Mashtots in the 5th century that distinguished Armenia from its Greek and Syriac counterparts. These reforms included a retranslation of the Bible and a revised liturgy. During the Crusades and afterwards, missionary activity by the Latin Church influenced liturgical norms and induced some Armenians to join the Catholic Church. The modern Armenian Rite features elements and interpolations from the Byzantine Rite and Latin liturgical rites, with the celebration of the Eucharist emulating the Liturgy of Saint Basil.