Matrix Basic Definitions

Square Matrix :

Any matrix that has equal number of rows and columns is called square matrix. E.g: 2x2, 3x3 matrix.

Diagonal Matrix :

A Diagonal matrix is a square matrix with numbers on the leading diagonal and zeros in all other places.

Identity Matrix :

An identity matrix is a square matrix denoted as I. It has ones (1) down the leading diagonal and zeros in all other places.

Note: Any matrix multiplied by its identity matrix leaves the matrix unchanged. It is similar to multiplying a number by 1. i.e AI = A (where A is a matrix)

Zero (Null) Matrix :

A zero or null matrix is a matrix with 0 as the element for all its cells (rows and columns).

Symmetric Matrix :

A symmetric matrix is a matrix where a_ij = a_ji. i.e an element at the i^th row, j^th columns should be equal to the element at the j^th row, i^th columns.

Equality Matrix :

For any two matrices to be said as equal matrices they should be of same size and have same values.