Identity Permutation
If $$I$$ is a permutation of degree $$n$$ such that $$I$$ replaces each element by the element itself, $$I$$ is called the identity permutation of degree $$n$$. Thus
\[I = \left( {\begin{array}{*{20}{c}}1&2&3& \cdots &n \\ 1&2&3& \cdots &n \end{array}} \right)\]
or
\[I = \left( {\begin{array}{*{20}{c}}{{a_1}}&{{a_2}}&{{a_3}}& \cdots &{{a_n}} \\ {{a_1}}&{{a_2}}&{{a_3}}& \cdots &{{a_n}} \end{array}} \right)\]
or
\[I = \left( {\begin{array}{*{20}{c}}{{b_1}}&{{b_2}}&{{b_3}}& \cdots &{{b_n}} \\ {{b_1}}&{{b_2}}&{{b_3}}& \cdots &{{b_n}} \end{array}} \right)\]
is the identity permutation of degree $$n$$.
For example, $$I = \left( {\begin{array}{*{20}{c}}1&2&3&4&5&6&7&8 \\ 1&2&3&4&5&6&7&8 \end{array}} \right)$$ is the identity permutation of $$X = \left\{ {1,2,3,4,5,6,7,8} \right\}$$