Koinonia in the context of "Catholicos of All Armenians"

Excommunication is an institutional act of religious censure used to deprive, suspend, or limit membership in a religious community or to restrict certain rights within it, in particular those of being in communion with other members of the congregation, and of receiving the sacraments.

It is practiced by all of the ancient churches (such as the Catholic Church, Oriental Orthodox churches and the Eastern Orthodox churches) as well as by other Christian denominations; however, it is also used more generally to refer to similar types of institutional religious exclusionary practices and shunning among other religious groups. The Amish have also been known to excommunicate members that were either seen or known for breaking rules, or questioning the church, a practice known as shunning. Jehovah's Witnesses use the term disfellowship to refer to their form of excommunication.

A Christian denomination is a distinct religious body within Christianity that comprises all church congregations of the same kind, identifiable by traits such as a name, particular history, organization, leadership, theological doctrine, worship style and, sometimes, a founder. It is a secular and neutral term, generally used to denote any established Christian church. Unlike a cult or sect, a denomination is usually seen as part of the Christian religious mainstream. Most Christian denominations refer to themselves as churches, whereas some newer ones tend to interchangeably use the terms churches, assemblies, fellowships, etc. Divisions between one group and another are defined by authority and doctrine; issues such as the nature of Jesus, the authority of apostolic succession, biblical hermeneutics, theology, ecclesiology, eschatology, and papal primacy may separate one denomination from another. Groups of denominations—often sharing broadly similar beliefs, practices, and historical ties—are sometimes known as "branches of Christianity". These branches differ in many ways, especially through differences in practices and belief.

Individual denominations vary widely in the degree to which they recognize one another. Several groups say they are the direct and sole authentic successor of the church founded by Jesus Christ in the 1st century AD. Others, however, believe in denominationalism, where some or all Christian groups are legitimate churches of the same religion regardless of their distinguishing labels, beliefs, and practices. Because of this concept, some Christian bodies reject the term "denomination" to describe themselves, to avoid implying equivalence with other churches or denominations.

In the canon law of the Catholic Church, excommunication (Lat. ex, "out of", and communio or communicatio, "communion"; literally meaning "exclusion from communion") is a form of censure. In the formal sense of the term, excommunication includes being barred not only from the sacraments but also from the fellowship of Christian baptism. The principal and severest censure, excommunication presupposes guilt; and being the most serious penalty that the Catholic Church can inflict, it supposes a grave offense. The excommunicated person is considered by Catholic ecclesiastical authority as an exile from the Church, for a time at least.

Excommunication is intended to invite the person to change behaviour or attitude, repent, and return to full communion. It is not an "expiatory penalty" designed to make satisfaction for the wrong done, much less a "vindictive penalty" designed solely to punish. Excommunication, which is the gravest penalty of all, is always "medicinal".

Church attendance is a central religious practice for many Christians; some Christian denominations require church attendance on the Lord's Day (Sunday).

In addition to being based upon the spirit of the Ten Commandments ("Remember the Sabbath day, to keep it holy"), the importance of church attendance in Christian theology is delineated in Hebrews 10:25, which implores the believers: "Let us not neglect our church meetings, as some people do, but encourage and warn each other, especially now that the day of his coming back again is drawing near." Certain early Christian saints emphasized the necessity of church attendance for the continuance of the faith, such as John Climacus, who declared that "a sure sign of the deadening of the soul is the avoidance of church services." The Lutheran theologian Balthasar Münter [da] stated that church attendance is the "foundation for the Christian life" as "the Christian Bible and the sacraments provide the framework for the faith"; he also states that it is important for believers because it aids in the prevention of backsliding, as well as offers "the company of other believers". The Catholic Church teaches that on Sundays and other holy days of obligation, the faithful are required to attend Mass. The Westminster Confession of Faith held by many Reformed Churches teaches first-day (Sunday) Sabbatarianism and the duty of church attendance on this day. Similarly, Methodist Church also requires attending "the public worship of God".