A graph vertex in a graph is said to be an even node if its vertex degree is even.
Even Vertex
See also
Graph, Graph Vertex, Odd Vertex, Vertex DegreeExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Even Vertex." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/EvenVertex.html