Game concept
Republic
The game also links it as Republics, Republican, Republican Government.
From the game's encyclopedia
Republican Government is an unplayable Government Form where an elected citizen rules for life — the Government Form of burghers and merchants.
Republican Vassals have static Obligations that cannot be changed, and thus always provide a dependable and predictable amount of Levies and Taxes.
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.
Republic is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "Republican Government is an unplayable Government Form where an elected citizen rules for life — the Government Form of burghers and merchants." It is part of Government. The game also links it as Republics, Republican and Republican Government. 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.