In
graph theory
In mathematics, graph theory is the study of ''graphs'', which are mathematical structures used to model pairwise relations between objects. A graph in this context is made up of '' vertices'' (also called ''nodes'' or ''points'') which are conne ...
, the outer boundary of a
subgraph of a
graph is the set of
vertices of not in that have a common
edge with a vertex in . Its inner boundary is the set of vertices of that have a common edge with a vertex not in . The edge boundary of , denoted by , is the set of ''edges'' between a vertex in and a vertex not in .
Graph theory
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