Katholikon

A katholikon or catholicon (Greek: καθολικόν) or sobor (Slavonic: съборъ) refers to one of three things in the Eastern Orthodox Church:

The main church of the monastery
Generally, the catholicon is named after the saint (or feast) to which the monastery is dedicated. But this is not an absolute rule. The catholicon must be located in the center of the perimeter, often quadrangular, according to which are ordered the different monastic buildings. The refectory is often located near the main entrance of the catholicon, to the west, because the monks often pass in solemn procession from one place to another.

This term catholicon is not used by Byzantine sources who simply use the term meaning church (naos or ekklesia).

The liturgy can only take place once a day on the same altar. This is the reason why monasteries frequently have several small secondary churches and chapels in addition to the catholicon.

Catholikon and kyriakon
The catholicon is only found in a monastery. The main church of a skite, monastic house or village, is called a kyriakon, a term that gave the words “church” (Kirche, church, kerke, kirke) in the different Germanic languages.

Catholicon and Katholiki ekklesia
The catholicon, which is a monastic church, should not be confused with the katholiki ekklesia (literally “catholic church”) which is a large orthodox church that had to be built in the center of a city to accommodate the influx of worshipers. when the cathedral title was estimated to be too small.

This is the case of the current city of Limassol in Cyprus which has two cathedrals, a very small and one of medium size as well as a larger church called “katholiki”. For an obvious reason, the term is not passed in the French language. He is the equivalent of Russian sobor.

Canon 59 of the Council in Trullo, held in 691, stipulates that baptisms must be celebrated in the katholikai ekklesiai : the term already designates the main churches of a bishopric.

The cathedral of a diocese.
The major church building (temple) of a monastery corresponding to a conventual church in Western Christianity.
A large church in a city at which all the faithful of the city gather to celebrate certain important feasts rather than go to their local parish church.
The name derives from the fact that it is (usually) the largest church where all gather together to celebrate the major feast days of the liturgical year. In Russia, it is common for a katholikon to have a smaller church in the basement which can be more easily heated in the winter. A katholikon may have special architectural features in it, such as a kathedra (episcopal throne), or both an esonarthex (inner-narthex) and exonarthex (outer narthex), used for special services such as the Paschal vigil or a lity.

The word katholikon is often translated into English as cathedral rather than assembly and that can cause confusion. In Saint Isaac’s Cathedral in Saint Petersburg, Russia, for example, there is a placard in Russian and in English describing the building as having been “кафедральный собор”, rendered in English as the “cathedraly cathedral”. However an Eastern Orthodox diocese may have several katholikons, only one of which is the bishop’s cathedral, other important churches being known as katholicons. The rector of such churches is usually an archpriest.

Source from Wikipedia