Boundary lines are defined markers that separate different areas or regions. They can be physical, like fences or walls, or abstract, such as legal or political borders. Boundary lines help establish ownership, jurisdiction, and responsibilities between different entities, such as countries, states, or properties. In geography, boundary lines are crucial for understanding maps and territories. For example, the boundary line between two countries, like Canada and the United States, determines where one nation's laws and governance end and another's begin. These lines can change over time due to treaties, conflicts, or negotiations, reflecting the dynamic nature of human relationships and governance.