Order of automorphism of nontrivial finite group is less than order of group

Definition
Suppose $$G$$ is a nontrivial finite group and $$\varphi$$ is an automorphism of $$G$$. Then, the order of $$\varphi$$, i.e., the order of the cyclic subgroup of $$\operatorname{Aut}(G)$$ generated by $$\varphi$$, is strictly less than the order of $$G$$.