• Stephen Wolfram Writings / Expression Evaluation and Fundamental Physics

Wikipedia

• Well-formed formula (WFF) often simply formula, is a finite sequence of symbols from a given alphabet that is part of a formal language.
• Propositional formula is a type of syntactic formula which is well formed and has a truth value.
• Rewriting covers a wide range of methods of replacing subterms of a formula with other terms.
• Floral formula is a notation for representing the structure of particular types of flowers.