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Let $\FF$ be a formal language whose alphabet is $\AA$.
A well-formed formula is a collation in $\AA$ which can be built by using the rules of formation of the formal grammar of $\FF$.
That is, a collation in $\AA$ is a well-formed formula in $\FF$ if and only if it has a parsing sequence in $\FF$.
Also known as
This is often encountered in its abbreviated form WFF, pronounced something like woof or oof, depending on personal preference.
Other names include well-formed word or simply formula.
Some less formal approaches use the term statement form.
(Well-formed) expression is also seen.
- 1959: A.H. Basson and D.J. O'Connor: Introduction to Symbolic Logic (3rd ed.) ... (previous) ... (next): $\S 4.1$: The Purpose of the Axiomatic Method
- 1965: E.J. Lemmon: Beginning Logic ... (previous) ... (next): Chapter $2$: The Propositional Calculus $2$: $1$ Formation Rules (in the context of the language of propositional logic)
- 1993: M. Ben-Ari: Mathematical Logic for Computer Science ... (previous) ... (next): Chapter $2$: Propositional Calculus: $\S 2.2$: Propositional formulas
- 2000: Michael R.A. Huth and Mark D. Ryan: Logic in Computer Science: Modelling and reasoning about systems ... (previous) ... (next): $\S 1.3$: Propositional logic as a formal language
- 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): well-formed formula
- 2012: M. Ben-Ari: Mathematical Logic for Computer Science (3rd ed.) ... (previous) ... (next): $\S 2.1$