It's also used in the theory of formal grammars, where terminal symbols (constants) are lower case, and non-terminal symbols (variables) are upper case: https:/

It's also used in the theory of formal grammars, where terminal symbols (constants) are lower case, and non-terminal symbols (variables) are upper case: https://en.wikipedia.org/wiki/Formal_grammar#Introductory_example https://en.wikipedia.org/wiki/Formal_grammar#Introductory_ex...