An unordered pair representation is a representation of an undirected graph in which edges are specified as unordered pairs of vertex indices. The
unordered pairs representation of an undirected graph 
may be computed in the Wolfram Language
using List @@@ EdgeList[g],
and a graph may be constructed from an unordered pair representation 
using Graph[UndirectedEdge @@@ l].
Unordered Pairs Representation
See also
Ordered Pairs Representation, Undirected GraphExplore with Wolfram|Alpha
References
Skiena, S. "Ordered Pairs." §3.1.3 in Implementing Discrete Mathematics: Combinatorics and Graph Theory with Mathematica. Reading, MA: Addison-Wesley, pp. 87-88, 1990.Cite this as:
Weisstein, Eric W. "Unordered Pairs Representation." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/UnorderedPairsRepresentation.html