Ahas some kind of unity in terms of terrain, climate, government, language and so on

Region

Explanation:

Region is a geographical area that is divided into sections such as physical, human and environmental geography, and it crates interaction between humanity and the environmental set up. It can also be used in different geographical areas that have limited access to government funding. However, regions have a relevant feature with language, climate or even terrains

The parts are typically characterized by unique and distinct properties from both the outside and inside. The sub-regions are also defined by the transitional boundaries which are different from the law.