\begin{definition}[Definition:Insertion of Generators]
Let $S$ be a set, and let $S^*$ be its Kleene closure.
The '''insertion of generators (into $S^*$)''' is the mapping $i: S \to S^*$ defined by:
:$i \left({s}\right) := \left\langle{s}\right\rangle$
that is, it sends any element $s$ of $S$ to the one-term sequence containing only $s$.
\end{definition}