Aregion with clearly defined borders is called a

Formal region

Explanation:

A formal region is one that is defined clearly by a structure such as the government. These type of regions have very clear boundaries, and include places such as cities, counties, countries, towns and states. Formal regions can often nest inside one another (a city is within a state, which in turn is located within a country).

byzantine empire is the answer i think you are looking for.

hope this : )

keeping a cash reserve because cash flow is the the movement of money through a company and if it just sits there, it wont the movement