The graph neighborhood of a graph vertex is terminology whose convention must be specified. The open graph neighborhood
consists of the vertices adjacent to
, excluding
itself. The closed neighborhood
also includes
. Some sources use "graph neighborhood"
specifically for
,
while others use "neighborhood" for
.
More generally, the th
neighborhood of
is the set of all vertices at graph distance
from
.
The subgraph induced by the neighborhood of a graph from vertex
is called the neighborhood graph.
The term "graph neighbors" generally means vertices adjacent to excluding
itself (Brouwer et al. 1989).