\begin{definition}[Definition:Series/Number Field]
Let $S$ be one of the standard number fields $\R$, or $\C$.
Let $\sequence {a_n}$ be a sequence in $S$.
The '''series''' is what results when $\sequence {a_n}$ is summed to infinity:
:$\ds \sum_{n \mathop = 1}^\infty a_n = a_1 + a_2 + a_3 + \cdots$
\end{definition}