What is Formal grammar?
A '''formal grammar''' says how to form an expression or a word, that is valid in a [[formal language]]. In the 1950s, [[Noam Chomsky]] classified formal grammars, into what is known as [[Chomsky hierarchy]] today: There are four different types of such grammars, numbered 0 to 3. Higher level grammars are stricter than lower level grammars. {{math-stub}} [[Category:Theoretical computer science]]