\begin{definition}[Definition:Almost All/Set Theory/Countable]
Let $S$ be a countably infinite set.
Let $P: S \to \left\{ {\text{true}, \text{false} }\right\}$ be a property of $S$ such that:
:$\left\{ {s \in S: \neg P \left({s}\right)}\right\}$
is finite.
Then $P$ holds for '''almost all''' of the elements of $S$.
Category:Definitions/Set Theory
\end{definition}