\begin{bmatrix} 0 & 0 & 0 \\ 0 & 0 & 0 \end{bmatrix} .\ The set of m &times; n matrices with entries in a ring K forms a ring K_{m,n} \,. The zero matrix 0_{K_{m,n}} \, in K_{m,n} \, is the matrix with all entries equal to 0_K \, ,