Game concept
Province
The game also links it as Provinces, Provincial, Theme, Themes, Thematic, Circuit, Circuits.
From the game's encyclopedia
A Province is a Title held by a Governor inside a Bureaucratic Realm.
A Province has an associated Province Administration that greatly impacts the benefits the Province provides.
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.
Province is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "A Province is a Title held by a Governor inside a Bureaucratic Realm." It is part of Administrative. The game also links it as Provinces, Provincial, Theme, Themes and 3 more. Patch 1.20.1.2, from game/common/game_concepts/07_ep3_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/07_ep3_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.