Well-formed

Last updated April 28, 2019

Well-formed or wellformed indicate syntactic correctness and may refer to:

Well-formedness, quality of linguistic elements that conform to grammar rules
Well-formed formula, a string that is generated by a formal grammar in logic
Well-formed element, web design element that is properly designed and ordered
Well-formed document, XML document that adheres to the syntax rules of the XML 1.0 specification
Well-formed Petri net, a Petri net class
Well-formed scale, a class of musical scales

Well-formedness is the quality of a clause, word, or other linguistic element that conforms to the grammar of the language of which it is a part. Well-formed words or phrases are grammatical, meaning they obey all relevant rules of grammar. In contrast, a form that violates some grammar rule is ill-formed and does not constitute part of the language.

In mathematical logic, propositional logic and predicate logic, a well-formed formula, abbreviated WFF or wff, often simply formula, is a finite sequence of symbols from a given alphabet that is part of a formal language. A formal language can be identified with the set of formulas in the language.

In web page design, and generally for all markup languages such as SGML, HTML, and XML, a well-formed element is one that is either a) opened and subsequently closed, or b) an empty element, which in that case must be terminated; and in either case which is properly nested so that it does not overlap with other elements.

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