Let E = {e1, e2, ...em} be a finite set, and let F be a family of subsets of E: then F is a matroid if it satisfies
  • {ei} in F for each i,

  • if G is in F, and if H is a non-empty subset of G, then H is in F.

  • for each S that is a subset of E, if G and H are two members of F contained in S and maximal with this property, then |G|=|H|.

--back to combinatorics--