Boundary (plural: boundaries) may refer to: in mathematics, A Boundary's the closure minus the interior of a subset of a topological space The conditions of a boundary value problem in Mathematics Boundary, an edge in the topology of manifolds, as in the case of a 'manifold with boundary' Boundary (thermodynamic), the edge of a thermodynamic system across which heat, mass, or work can flow in other fields Boundaries in landscape history, the divide between areas of differing land use Bounda… (More on Boundary)