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well-formed formula

A string of symbols that counts as a sentence of the formal language.

A well-formed formula is any string built by the formation rules: every sentence letter is one; if A is one, so is its negation; if A and B are, so is each of their conjunction, disjunction, conditional, and biconditional, wrapped in brackets. Nothing else is.

Examples

  • (P ∧ Q) → R is well-formed.

  • P ∧ ∨ Q is not.

See also

scope main connective
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