Sentence diagramming is the long division of English. It involves a bewildering array of lines and diagonal branches. It is loathed as an elementary school chore. And it is presumed to be obsolete.

There are plenty of people out there—not only English teachers but also amateur language buffs like me—who believe that diagramming a sentence provides insight into the mind of its perpetrator. The ...

I read an article last month about the lost art of diagramming sentences, a once-required skill that many American children had to master if they wanted to pass English back in the mid-20th century.