periodic point of

Let a continuum X and a mapping $f: X \to X$ be given. For each natural number n denote by fⁿ the n-th iteration of f. A point $p \in X$ is called a periodic point of f provided that there is $n \in \mathbb{N}$ such that fⁿ(p) = p The set of periodic points of a mapping $f: X \to X$ are denoted by P(f).