Edge support of a graph
= Edge support of a graph
{title2=$G_+$}
For a finite undirected <multigraph> $G=(V,E)$, its <edge support of a graph> is the <subgraph> $G_+=(V_+,E)$ with $V_+=\{v\in V:\deg(v)>0\}$. It removes exactly the <isolated vertices>, retaining every <edge>, including <self-loops> and parallel <edges>. When $E\ne\varnothing$, connectivity of this <subgraph> is the relevant condition for an <Eulerian trail> or <Euler circuit>.