\begin{definition}[Definition:Relational Loop]
Let $\RR$ be a relation on a set $S$.
Let $a_1, a_2, \ldots a_n$ be elements of $S$.
A '''relational loop on $S$''' takes the form:
:$\tuple {a_1 \mathrel \RR a_2 \land a_2 \mathrel \RR a_3 \dots \land a_{n - 1} \mathrel \RR a_n \land a_n \mathrel \RR a_1}$
That is, it is a subset of $\RR$ of the form:
:$\set {\tuple {a_1, a_2}, \tuple {a_2, a_3}, \ldots, \tuple {a_{n - 1}, a_n}, \tuple {a_n, a_1} }$
\end{definition}