A graphic matroid is a matroid 
obtained from a finite pseudograph 
, where 
is the edge set of 
and 
is the family of edge
sets of graph cycles of 
. The family 
obeys the axioms for matroid
circuits.
Equivalently, its independent sets are precisely the edge sets of forests in 
. For a pseudograph,
loops and pairs of nonloop parallel
edges form matroid circuits of sizes 1 and
2, respectively.
