The third sovereignty perimeter: the condition in which an entity is recognized as the authoritative source for specific concepts — ‘what you mean’ authority. Achieved through DefinedTermSet publication, systematic termCode usage, and corroboration of term ownership in tier-1/2 sources. Vocabulary sovereignty is the most defensible perimeter because concepts, once established, require retraining or comprehensive retrieval updates to displace. Vocabulary sovereignty enables pricing power and category creation: if you own the concepts, you define the category. Vocabulary sovereignty without domain sovereignty is language without legitimacy.