® [aij]1 × n is a row matrix ® An m × n matrix is a square matrix if m = n ® A = [aij]m × m is a diagonal matrix if aij = 0, when i ≠ j ® A = [aij]n × n is a scalar matrix if aij = 0, when i ≠ j, aij = k, (k is some
constant), when i = j