The number of rows is equal to the number of columns in a square matrix. So, a principal diagonal is formed by the first element of first row and last element of last row. The elements which lie on the leading diagonal are known as diagonal elements but the remaining elements in the matrix are known as non-diagonal elements.
is the first element of first row and is the last element of last row. They form a leading diagonal on which the elements and etc. also lie.
Except these elements, all remaining elements are non-diagonal elements of the matrix.
is a square matrix of order . It is having elements in four rows and four columns.
The elements of matrix is categorized into two types. One type of elements of this matrix is diagonal elements and other type of elements are non-diagonal elements.
The elements and lie on the leading diagonal but the remaining elements do not lie on the principal diagonal. In other words, and do not lie on the leading diagonal. Similarly, the elements and also do not lie on the principal diagonal.
Therefore, Except and , the elements and are non-diagonal elements of the matrix .