Game concept
Clerical Region
The game also links it as Clerical Regions, Clerical Region's, Clerical Regions'.
From the game's encyclopedia
A Clerical Region is a geographical region that falls under the jurisdiction of a Clerical Title. Any member of the clergy within the region will be a Subordinate to the holder of the Title associated with the region.
A Ruler belongs to the Clerical Region that contains their Capital County, and a new region is founded upon the Capital of its founder's Primary Title. The region may cover multiple Realms and have subordinates that are in different realms.
A Ruler may only hold one Clerical Region at a time. If granted a new Region, the Ruler forfeits all their held land within the previous one.
The game's text for patch 1.20.1.2. Words in blue are entries of the encyclopedia: hover one to read it, as in the game.
Clerical Region is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "A Clerical Region is a geographical region that falls under the jurisdiction of a Clerical Title." It covers Clerical Region Capital. The game also links it as Clerical Regions, Clerical Region's and Clerical Regions'. Patch 1.20.1.2, from game/common/game_concepts/pam_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/pam_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.