  The aim of this paper is to generalize the $m-$Segre invariant for vector
bundles to coherent systems. Let $X$ be a non-singular irreducible complex
projective curve of genus $g$ over $\mathbb{C}$ and $(E,V)$ be a coherent
system on $X$ of type $(n,d,k)$. For any pair of integers $m, t$, $0 < m < n$,
$0 \leq t \leq k$ we define the $(m,t)-$Segre invariant, denoted by
$S^\alpha_{m,t}$ and show that $S^\alpha_{m,t}$ induces a semicontinuous
function on the families of coherent systems. Thus, $S^\alpha_{m,t}$ gives a
stratification of the moduli space $G(\alpha;n,d,k)$ of $\alpha-$stable
coherent systems of type $(n,d,k)$ on $X$ into locally closed subvarieties
$G(\alpha;n,d,k;m,t;s)$ according to the value $s$ of $S^\alpha_{m,t}$. We
study the stratification, determine conditions under which the different strata
are non-empty and compute their dimension.
