Today we recur to fundamental questions: What is a writer’s duty to his readers? And what is a writer’s duty to herself? We’re off again on the intractable topic of Hard Words.

First, we’re not talking about fiction. In that genre, an author’s first obligation is to hold his readers captive to his characters and his plot. Many authors who can write delightful novels would be flops at covering political debate. Neither are we talking about writing in specialized fields of prose composition. The English language has hundreds – probably thousands – of sub-vocabularies, ranging from astrology to zoology.

Today’s meditation has to do with our most common means of written communication, the daily newspaper and the weekly magazine. We begin by assuming a plausible goal, that 92 percent of our readers will understand 92 percent of what we write. To aim at 100 percent comprehension is to aim at a diet of mush. If we write down to our readers, our readers will loathe us and leave us. We cannot abandon hard words altogether. But what hard words are too hard?

Several years ago, The New York Times reviewed a new TV show called “Less Than Perfect.” The critic explained: “It marks the first time that a network cast as a nubile lead a relatively unknown actress because she was zaftig, and not despite it.”

Would 92 percent of the Times’ readers know that to be nubile is to be sexually attractive, and that to be zaftig is to be well-rounded, plump?

My next-to-favorite columnist is Maureen Dowd of The New York Times. She often tries too hard to hit every phrase out of the park, but she never talks down to us: “The hawks saw their big chance after Sept. 11, but they feared it would be hard to sell an eschatological scheme to stomp our Islamic terror.” How firmly do you grasp an eschatological scheme?

During his tenure as secretary of homeland security, Tom Ridge was asked about his color-coded system of classifying terrorist alerts. He agreed that it needed refinement in order to reach “a word they like to use in intelligence, ‘granularity.”‘ The word evidently is a spook-speak derivative from “granule,” that is, “one of numerous particles forming a larger unit.”

A couple of years ago, columnist Nicholas Kristof recalled a summer in France when his boss constantly denounced the English as overly “penible.” Kristof tracked down the adjective in the Oxford English Dictionary. It means “painstaking, careful; causing or involving pain or trouble.” At least that’s what it meant in the 17th century. Send it back?

What about “zhlub”? In New York magazine, a film critic identified a player in the comedy “Sideways” as “a glum zhlub.” Leo Rosten, to the rescue! In Yiddish, a zhlub is a fellow who is coarse, ill-mannered, clumsy, graceless. Was this word necessary to the review? It pleased the critic. Did it mystify many readers? Does that matter?

This past November, when I was ruminating on hard words, a reader in Binghamton, N.Y. sent me a note. He recalled a restaurant critic who remarked upon a dinner that was “extremely good though somewhat costive.” How’s that again? Costive? The obsolete adjective dates from the 14th century. He should have looked it up. And left it there.

James Kilpatrick is a syndicated columnist.