Game concept
Prison
The game also links it as Imprisons, Imprison, Imprisoned, Prisons, Imprisoning, Imprisonment, Prisoner, Prisoners, Jailor.
From the game's encyclopedia
Landed Rulers can keep other Characters as Prisoners, either in their Dungeon or under simple House Arrest. In a Camp all Prisoners are kept in the Stockade. Characters risk imprisonment in Battle or at the end of a Siege.
Characters can also arrest anyone inside their own Realm, or Camp. However, this is viewed as Tyrannical unless the Character is guilty of a Crime.
Prisoners are at your mercy and can be Executed, Tortured, Ransomed or simply Released.
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.
Prison is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "Landed Rulers can keep other Characters as Prisoners, either in their Dungeon or under simple House Arrest." It covers Dungeon, Stockade and House Arrest. The game also links it as Imprisons, Imprison, Imprisoned, Prisons and 5 more. Patch 1.20.1.2, from game/common/game_concepts/00_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/00_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.