The meaning of identity is oneness. So, identity matrix is having elements on the leading diagonal but all the elements should be same. There is also another meaning for identity and it is unity. The meaning of unity is number . Therefore, all diagonal elements are in an identity matrix. Hence, an identity matrix is also called as a unit matrix.
Identity matrix is denoted by a letter in mathematics. It is a square matrix. It means, the number of rows and number of columns are equal. Therefore, order of matrix is expressed as subscript to the letter as per the concept of order representation of square matrix. If number of rows and number of columns are , the identity matrix is denoted by in mathematics.
An identity matrix is read in one of three following methods.
It is an identity matrix of order .
It is a second order identity matrix.
It is a rowed identity matrix.