Game concept
Hybrid Culture
The game also links it as Hybrid Cultures, Hybridize, Hybridized, Hybridizing, Hybridizes.
From the game's encyclopedia
A Hybrid Culture is a Culture that was created by a Ruler as the combination of two existing Cultures.
The Hybrid Culture is a mixture of the two original Culture's Traditions, Cultural Pillars, and Aesthetics.
Only Cultures of different Heritage can form a Hybrid, and the Prestige cost to do so is based on their Cultural Acceptance of each other.
The higher the Cultural Acceptance, the more Counties will convert when a Hybrid forms. Rulers of a Hybrid culture Promote Culture much faster in Counties of its parent cultures for -9950–100 years after it forms.
New Cultures can also appear as a Divergent Culture.
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.
Hybrid Culture is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "A Hybrid Culture is a Culture that was created by a Ruler as the combination of two existing Cultures." It is part of Culture. The game also links it as Hybrid Cultures, Hybridize, Hybridized, Hybridizing and 1 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.