A matrix is an ordered rectangular array of numbers or functions. A matrix having m rows and n columns is called a matrix of order m × n.
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 zero matrix has all its elements as zero.
A is a symmetric matrix if A′ = A.
A is a skew symmetric matrix if A′ = -A.
Any square matrix can be represented as the sum of a symmetric and a skew symmetric matrix.
If A and B are two square matrices such that AB = BA = I, then B is the inverse matrix of A and is denoted by A-1 and A is the inverse of B.