Editing Cyclomatic number (section)

{{Short description|Fewest graph edges whose removal breaks all cycles}}
{{for|related notion called cycle rank in directed graphs|cycle rank}}
[[File:6n-graf.svg|thumb|upright=1.3|This graph has cyclomatic number {{math|1=''r'' = 2}} because it can be made into a tree by removing two edges, for instance the edges 1–2 and 2–3, but removing any one edge leaves a cycle in the graph.]]
In [[graph theory]], a branch of [[mathematics]], the '''cyclomatic number''', '''circuit rank''', '''cycle rank''', or '''nullity''' of an [[undirected graph]] is the minimum number of  edges that must be removed from the graph to break all its [[cycle (graph theory)|cycle]]s, making it into a [[tree (graph theory)|tree]] or [[forest (graph theory)|forest]].