The set of edges of a loopless graph , being a set of unordered pairs of elements of , constitutes an adjacency relation on . Formally, an adjacency relation is any relation which is irreflexive and symmetric.
See alsoIrreflexive, Relation, Symmetric
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Cite this as:
Weisstein, Eric W. "Adjacency Relation." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/AdjacencyRelation.html