In the Rule of St. Benedict, the term 'prior' occurs several times, but does not signify any particular superior; it is indiscriminately applied to any superior, be he the Abbot, Provost, Dean, etc. In other old monastic rules the term is used in the same generic sense. With the Cluniac reform the term Prior received a specific meaning; it supplanted the provost (praepositus) of the Rule of St. Benedict.
The example of the Cluniac congregations was gradually followed by all Benedictine monasteries, as well as by the Camaldolese, Vallombrosians, Cistercians, Hirsau congregations, and other offshoots of the Benedictine Order.
Monastic congregations of hermit origin generally do not use the title of abbot for the head of any of their houses, in an effort to avoid the invovlement with the world the office of an abbot would entail. As a result, it is not in use for the congregation as a whole. Among them, the equivalent term of Prior General is the one used. This applies, e.g., for the Camaldolese and the Carthusians.