Definition:Undirected Graph
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Definition
An undirected graph is a graph whose edge set considered as a relation is symmetric.
That is, if $G$ is an undirected graph and $e = uv$ is an edge in $G$, then $vu$ is also an edge in $G$.
vIn other words, if you can "go from $u$ to $v$", you can also "go from $v$ to $u$"
Compare with a directed graph, or digraph, whose edges (or arcs have a "direction", and such freedom is not guaranteed.
