Question

boundary

Accepted Answer

something (such as a river, a fence, or an imaginary line) that shows where an area ends and another area begins

Those two trees mark the boundary of our property.
The river forms the country's western boundary.

Front	boundary
Back	something (such as a river, a fence, or an imaginary line) that shows where an area ends and another area begins Those two trees mark the boundary of our property. The river forms the country's western boundary.

Boundary Area River Fence Imaginary Line Shows Ends