A 1-factor of a graph 
with 
graph vertices is a set of
separate graph
edges which collectively contain all 
of the graph vertices of 
among their endpoints.
Graph Factor
See also
GraphExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Graph Factor." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/GraphFactor.html