Ground set size
$n$ is the number of elements of the ground set $E$ of the matroid. Elements are numbered $1,\dots,n$. Together with the rank it determines the family a matroid belongs to, e.g. all rank-3 matroids on 8 elements.
$n$ is the number of elements of the ground set $E$ of the matroid. Elements are numbered $1,\dots,n$. Together with the rank it determines the family a matroid belongs to, e.g. all rank-3 matroids on 8 elements.