Game concept

Duke

The game also links it as Dukes.

From the game's encyclopedia

A Duke is a Ruler whose Primary Title is a Duchy.

Their Rank is directly above Counts and directly below Kings, and as such they can have Counts as Vassals, and a King or above as their Liege.

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.

Duke is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "A Duke is a Ruler whose Primary Title is a Duchy." It is part of rank. The game also links it as Dukes. Patch 1.20.1.2, from game/common/game_concepts/00_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.

for a guide, post or blog

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.