That's a decent measure of how complex a grammar is. It also highly hints that the language in question is at least context-free: you probably wouldn't use the

That's a decent measure of how complex a grammar is. It also highly hints that the language in question is at least context-free: you probably wouldn't use the word "nonterminal" to describe a regular language. (Unless you were specifying a language that happened to be regular as a context-free grammar, I suppose.)