\begin{definition}[Definition:Sequence of Distinct Terms]
A '''sequence of distinct terms of $S$''' is an injection from a subset of $\N$ into $S$.
Thus a sequence $\sequence {a_k}_{k \mathop \in A}$ is a '''sequence of distinct terms''' {{iff}}:
:$\forall j, k \in A: j \ne k \implies a_j \ne a_k$
Informally, a '''sequence of distinct terms''' is a sequence whose terms are pairwise distinct.
\end{definition}