Cycle graph

Example

Let $n \ge 3$ be an integer. The cycle graph $C_n$ is the graph with vertex set $\mathbb{Z}/n\mathbb{Z}$ in which $i$ and $j$ are adjacent if and only if $j - i = \pm 1$. Its edges are $\{0, 1\}, \{1, 2\}, \dots, \{n-2, n-1\}$ and $\{n-1, 0\}$.