1  Order of a matrix
A matrix having m rows and n columns is called a matrix of order m × n or simply m × n
matrix (read as an m by n matrix) So referring to the above examples of matrices, we
have A as 3 × 2 matrix, B as 3 × 3 matrix and C as 2 × 3 matrix We observe that A has
3 × 2 = 6 elements, B and C have 9 and 6 elements, respectively In general, an m × n matrix has the following rectangular array:
or
A = [aij]m × n, 1≤ i ≤ m, 1≤ j ≤ n   i, j ∈ N
Thus the ith  row consists of the elements ai1, ai2, ai3,