Church is a classificatory term used to describe the institutional expression of religion. Churches typically tolerate no religious competition, and serve as the guardians and guides of spiritual life for a particular group of people. Churches can be contrasted with denominations, which do involve competition between religions. A church, through its institutional presence, typically strives to provide an all-encompassing worldview for its adherents. It is also almost always enmeshed with the political and economic structures of a society. A striking historical example of this is the Holy Roman Empire.
A slight modification of the church type is that of ecclesia. Ecclesias include the above characteristics of churches, but they are generally less successful at garnering absolute adherence among all of the members of the society. Ecclesias are also typically not the sole religious body in a particular societal space. The state churches of some European nations would fit this type. State churches are organizational bodies within a Christian denomination that have been given official status by a state, or are directly operated by a state. The Anglican Church of England, for example, is a state church that does not have the adherence of all English citizens. Because of this, it is considered an ecclesia.
An ecclesial community is, in Roman Catholic terminology, a Christian religious group that does not meet the Roman Catholic definition of a church. Although the word "ecclesial" itself stems from the Greek word for "church" or "gathering," ecclesias are not necessarily churches. The Catholic Church applies the word "Church" only to Christian communities that, in the view of the Catholic Church, "have true sacraments in light of Apostolic succession" and that possess a priesthood and the Eucharist. In this way, certain ecclesia fail to meet the requirements for a church. In Catholic canon law, a particular church is an ecclesial community headed by a bishop or an equivalent figure.