Size:
* Principality: A territory ruled by a prince or princess. This implies a smaller scale than a kingdom.
* Duchy: A territory ruled by a duke or duchess. Like a principality, it suggests a smaller size than a kingdom.
* County: A territory ruled by a count or countess. This is usually smaller than a duchy and more closely associated with medieval Europe.
* Barony: A territory ruled by a baron or baroness. Often smaller than a county.
Power:
* Mini-state: This implies a small and often independent state, perhaps with limited resources or power.
* Micronation: A self-proclaimed state that lacks international recognition, typically small in size and population.
Informal:
* Little kingdom: This is a straightforward and informal way to describe a small kingdom.
* Tiny realm: This emphasizes the small size of the kingdom.
The best word will depend on the context and the specific meaning you want to convey.