\begin{definition}[Definition:Classes of WFFs/Sentence]
Let $\LL_1$ be the language of predicate logic.
A WFF is said to be a '''sentence''' {{iff}} it contains no free variables.
To denote particular classes of '''sentences''', $\map {SENT} {\PP, \FF, \KK}$ and analogues may be used, similar to the notation for classes of WFFs.
\end{definition}