| context | $n_X,n_Y\in\mathbb N$ |
| definiendum | $ B \in \mathrm{it}(n_X,n_Y) $ |
| postulate | $ B \in \mathrm{Matrix}(n_X,n_Y,\mathbb N) $ |
If the indices $i,j$ label two vertices belonging to the partitions $X,Y$ of a finite bipartite graph, respectively, then the value $B_{ij}$ determines the number of edges joining them.