Definition:Classes of WFFs/Sentence
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Definition
Let $\mathcal L_1$ be the language of predicate logic.
A WFF is said to be a sentence if and only if it contains no free variables.
To denote particular classes of sentences, $SENT \left({\mathcal P, \mathcal F, \mathcal K}\right)$ and analogues may be used, similar to the notation for classes of WFFs.
Sources
- 1996: H. Jerome Keisler and Joel Robbin: Mathematical Logic and Computability: $\S 2.3$
- 2009: Kenneth Kunen: The Foundations of Mathematics ... (previous) ... (next): $\mathrm{II}.5$ First-Order Logic Syntax: Definition $\mathrm{II}.5.5$
