Game concept
House Unity Level
The game also links it as House Unity Levels.
From the game's encyclopedia
House Unity Level is the current state of House Unity. Active level changes as Unity increases through Unifying Actions or decreases through Divisive Actions, and each level provides the members of a House with various benefits and penalties.
There are five different levels:
GetCurrentHouseUnityStagesDescForLocalPlayer
Each level entails its own House Succession Law.
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.
House Unity Level is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "House Unity Level is the current state of House Unity." The game also links it as House Unity Levels. Patch 1.20.1.2, from game/common/game_concepts/03_fp3_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/03_fp3_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.