Definition:Rule of Formation

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Let $\FF$ be a formal language whose alphabet is $\AA$.

The rules of formation of $\FF$ are the rules which define how to construct collations in $\AA$ which are well-formed.

That is, the rules of formation tell you how to build collations featuring symbols from the alphabet $\AA$ which are part of the formal language $\FF$.

The rules of formation of a formal language together constitute its formal grammar.

There are no strict guidelines on what a rule of formation should look like, since they are employed to produce such strict guidelines.

Thus, these rules of formation are often phrased in natural language, and their exact form is to some extent arbitrary.


Not A

In the language of propositional logic, logical negation is implemented using the rule of formation:

$\mathbf W: \neg:$ If $\mathbf A$ is a WFF, then $\neg \mathbf A$ is a WFF.

Also known as

Rules of formation are also referred to in some sources as rules of syntax.

Some sources prefer the construct formation rules.

Also see

  • Results about rules of formation can be found here.