Though closely related, in this context "church" thus refers to the institution, and "rite" to its practices. Then again, there are two kinds of particular churches:
In Catholic ecclesiology, a church is an assembly of the faithful, hierarchically ordered, both in the entire world – the Catholic Church, or in a certain territory – a particular church. To be a sacrament (a sign) of the Mystical Body of Christ in the world, a church must have both a head and members (Col. 1:18). The sacramental sign of Christ the head is the sacred hierarchy – the bishops, priests and deacons. More specifically, it is the local bishop, with his priests and deacons gathered around and assisting him in his office of teaching, sanctifying and governing (Mt. 28:19–20; Titus 1:4–9). Thus, the church is fully present sacramentally (by way of a sign) wherever there is a sign of Christ the head, a bishop and those who assist him, and a sign of Christ's body, Christian faithful. Each diocese is therefore considered a particular church. On the worldwide level, the sign of Christ the head is the Pope, and, to be Catholic, particular churches, whether local churches or autonomous ritual churches must be in communion with this sign of Christ the head, Through this full communion with Saint Peter and his successors the church becomes a universal sacrament of salvation to the end of the age (Mt. 28:20).
The word "church" is applied to the Catholic Church as a whole, which is seen as a single church: the multitude of peoples and cultures within the church, and the great diversity of gifts, offices, conditions and ways of life of its members are not opposed to the church's unity. In this sense of "church", the list of churches in the Catholic Church has only one member, the Catholic Church itself (comprising Roman and Eastern Churches).
Within the Catholic Church there are local particular churches, of which dioceses are the most familiar form. Other forms include territorial abbacies, apostolic vicariates and apostolic prefectures. The Code of Canon Law states: "Particular Churches, in which and from which the one and only Catholic Church exists, are principally dioceses. Unless the contrary is clear, the following are equivalent to a diocese: a territorial prelature, a territorial abbacy, a vicariate apostolic, a prefecture apostolic and a permanently established apostolic administration." A list of Catholic dioceses, of which on 31 December 2011 there were 2,834, is given at List of Catholic dioceses (alphabetical).
Within the Catholic Church there are also aggregations of local particular churches that share a specific liturgical, theological, spiritual, and canonical heritage, distinguished from other heritages on the basis of cultural and historical circumstances. These are known as autonomous ("sui iuris") churches. The 1990 Code of Canons of the Eastern Churches defines such a church as follows: "A group of Christ's faithful hierarchically linked in accordance with law and given express or tacit recognition by the supreme authority of the Church is in this Code called an autonomous Church." There are 24 such autonomous Catholic churches: One Latin Church (i. e. Western) and 23 Eastern Catholic Churches", a distinction by now more historical than geographical. Although each of them has its own specific heritage, they are all in full communion with the Pope in Rome.