Game concept
Cultural Tradition
The game also links it as Cultural Traditions, Tradition, Traditions.
From the game's encyclopedia
Traditions represent the practices, habits, values, and ethics of individual Cultures.
Each Tradition grants some type of bonus or special ability to Characters or Counties of that Culture.
The Culture Head can establish new Traditions or replace existing ones for a Culture through Reformation.
Cultures can have up to 6 Traditions, but most have fewer.
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.
Cultural Tradition is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "Traditions represent the practices, habits, values, and ethics of individual Cultures." It is part of Culture. The game also links it as Cultural Traditions, Tradition and Traditions. 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.