Boundary or edge (9)
I believe the answer is:
periphery
I believe this is a double definition.
'boundary' is the first definition.
(I know that periphery is a type of boundary)
'edge' is the second definition.
(I know that periphery is a type of edge)
(Other definitions for periphery that I've seen before include "Surrounding region" , "Edge -- border" , "margin" .)