Game concept · The Royal Court
Court Language
The game also links it as Court Languages.
From the game's encyclopedia
A Court Language is the official Language of a Royal Court, spoken by the nobility and used by the bureaucracy.
The Court Grandeur Baseline is increased for each Realm County that shares the Language, for each Royal Court which speaks the same Court Language, and if it is the Ruler's native Language.
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.
Court Language is an entry of Crusader Kings III's in-game encyclopedia (The Royal Court). The game explains it: "A Court Language is the official Language of a Royal Court, spoken by the nobility and used by the bureaucracy." It is part of Language. The game also links it as Court Languages. Patch 1.20.1.2, from game/common/game_concepts/01_ep1_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/01_ep1_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.