\begin{definition}[Definition:Falsifiable/Formula]
Let $\LL$ be a logical language.
Let $\mathscr M$ be a formal semantics for $\LL$.
A logical formula $\phi$ of $\LL$ is '''falsifiable for $\mathscr M$''' {{iff}}:
:$\phi$ is not valid in some structure $\MM$ of $\mathscr M$
That is, there exists some structure $\MM$ of $\mathscr M$ such that:
:$\MM \not\models_{\mathscr M} \phi$
{{expand}}
\end{definition}