THE ancient notion of English grammar was one of certain categories of words, and certain rules for their proper use. This is still the idea implied in most of the dictionary definitions of the word.

The Oxford comma. “Ask” instead of “aks.” There, their, and they’re. The legitimacy of “ain’t” and “y’all.” These are familiar, if sometimes contentious, issues in the usage of the English language.

You’ve probably heard the old story about the pedant who dared to tinker with Winston Churchill’s writing because the great man had ended a sentence with a preposition. Churchill’s scribbled response: ...