The term 'defined region' can be summed up as a 'ZONE'. A ZONE is an area that has been divided into sections or parts for a specific purpose. It can refer to a geographical area, a political boundary, or a particular type of environment. Zones are often used to regulate activities within a certain area, such as zoning laws that restrict the types of buildings that can be built in a certain area. Zones can also be used to protect certain areas from development or to preserve natural resources.