Game concept
Army
The game also links it as Armies.
From the game's encyclopedia
Armies are used to win Wars by engaging in Battle with other armies, and to Besiege and Occupy enemy Fortified Holdings. Armies are raised in Rally Points and primarily consist of Levies and Men-at-Arms, but can also be bolstered by Mercenaries and Holy Orders.
Armies can move across water by spending an amount of Gold to secure transport. They can suffer losses from Attrition if the local Barony is unable to adequately Supply them.
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.
Army is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "Armies are used to win Wars by engaging in Battle with other armies, and to Besiege and Occupy enemy Fortified Holdings." The game also links it as Armies. 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.