This paper defines and discusses the dimension notion of topological slow entropy of any subset for Z d −actions. Also, the notion of measure-theoretic slow entropy for Z d −actions is presented, which is modified from Brin and Katok (Geometric Dynamics, Springer, Berlin 1983). Relations between Bowen topological entropy Bowen (Trans Am Math, 184:125-136, 1973), and topological slow entropy are studied in this paper, and several examples of the topological slow entropy in a symbolic system are given. Specifically, a variational principle is proved.