\begin{definition}[Definition:Contingent Statement]
A '''contingent statement''' is a statement form which is neither a tautology, nor unsatisfiable, but whose truth value depends upon the truth value of its component substatements.
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== Formal Definition ==
Let $\mathfrak M$ be a collection of models for a particular formal language $\LL$.
A well-formed word $\mathbf A$ of $\LL$ is said to be '''contingent (for $\mathfrak M$)''' {{iff}}:
:$\exists \MM_1, \MM_2 \in \mathfrak M: \MM_1 \models \mathbf A \land \MM_2 \not \models \mathbf A$
that is, {{iff}} some models in $\mathfrak M$ approve, and others disapprove of $\mathbf A$.
== Also known as ==
{{refactor|Seems to be replaceable by Also see entries. But, will need source review}}
In the context of propositional formulas the term '''satisfiable''' is usually used:
A propositional formula is '''satisfiable''' if its value is True in at least ''one'' boolean interpretation.
A propositional formula is '''not-valid''' or '''falsifiable''' if its value is False in at least ''one'' boolean interpretation.
\end{definition}