\begin{definition}[Definition:Formal Semantics]
Let $\LL$ be a formal language.
A '''formal semantics''' for $\LL$ comprises:
* A collection of objects called '''structures''';
* A notion of '''validity''' of $\LL$-WFFs in these structures.
Often, a '''formal semantics''' provides these by using a lot of auxiliary definitions.
\end{definition}