Boundary loop
= Boundary loop
A <boundary loop> travels around a boundary <circle> of a <topological surface>. To regard it as an element of the <fundamental group> at a <base point> away from the boundary, join that <base point> to the boundary by a <path>, go around the boundary, and follow the reverse <path>. Changing that joining <path> conjugates the element; reversing the boundary orientation inverts it.