A boundary line refers to a demarcation that separates one area or territory from another. It can be physical, like a river or mountain range, or it can be an imaginary line agreed upon by countries.
Related terms
Border: A border is a specific type of boundary that separates two political entities, such as countries or states.
Delimitation: Delimitation is the process of physically marking and establishing boundaries on the ground.
Demarcation: Demarcation is the act of setting clear and visible markers along a boundary to indicate its location.