<span>glass, air, plastic, rubber</span>
I believe the answer is: Formal region
Each formal region would be differentiated by their own unique government structure that separate each region with the other. Each border on the sides of each region would consist of some sort of boundaries ( could be natural or human made) that accepted by all regions as a legal separation between their jurisdiction.
Answer:
Far western of nepal like kanchanpur, doti, bajang
