By SAM ROBERTS
Correction Appended

It was nearly hidden on a New York City Transit public service placard exhorting subway riders not to leave their newspaper behind when they get off the train.

“Please put it in a trash can,” riders are reminded. After which Neil Neches, an erudite writer in the transit agency’s marketing and service information department, inserted a semicolon. The rest of the sentence reads, “that’s good news for everyone.”

Semicolon sightings in the city are unusual, period, much less in exhortations drafted by committees of civil servants. In literature and journalism, not to mention in advertising, the semicolon has been largely jettisoned as a pretentious anachronism.

Americans, in particular, prefer shorter sentences without, as style books advise, that distinct division between statements that are closely related but require a separation more prolonged than a conjunction and more emphatic than a comma.

“When Hemingway killed himself he put a period at the end of his life,” Kurt Vonnegut once said. “Old age is more like a semicolon.”

In terms of punctuation, semicolons signal something New Yorkers rarely do. Frank McCourt, the writer and former English teacher at Stuyvesant High School, describes the semicolon as the yellow traffic light of a “New York sentence.” In response, most New Yorkers accelerate; they don’t pause to contemplate.

Semicolons are supposed to be introduced into the curriculum of the New York City public schools in the third grade. That is where Mr. Neches, the 55-year-old New York City Transit marketing manager, learned them, before graduating from Tilden High School and Brooklyn College, where he majored in English and later received a master’s degree in creative writing.

But, whatever one’s personal feelings about semicolons, some people don’t use them because they never learned how.

In fact, when Mr. Neches was informed by a supervisor that a reporter was inquiring about who was responsible for the semicolon, he was concerned.

“I thought at first somebody was complaining,” he said.

One of the school system’s most notorious graduates, David Berkowitz, the Son of Sam serial killer who taunted police and the press with rambling handwritten notes, was, as the columnist Jimmy Breslin wrote, the only murderer he ever encountered who could wield a semicolon just as well as a revolver. (Mr. Berkowitz, by the way, is now serving an even longer sentence.)

But the rules of grammar are routinely violated on both sides of the law.

People have lost fortunes and even been put to death because of imprecise punctuation involving semicolons in legal papers. In 2004, a court in San Francisco rejected a conservative group’s challenge to a statute allowing gay marriage because the operative phrases were separated incorrectly by a semicolon instead of by the proper conjunction.

Louis Menand, an English professor at Harvard and a staff writer at The New Yorker, pronounced the subway poster’s use of the semicolon to be “impeccable.”

Lynne Truss, author of “Eats, Shoots & Leaves: The Zero Tolerance Approach to Punctuation,” called it a “lovely example” of proper punctuation.

Geoffrey Nunberg, a professor of linguistics at the University of California, Berkeley, praised the “burgeoning of punctuational literacy in unlikely places.”

Allan M. Siegal, a longtime arbiter of New York Times style before retiring, opined, “The semicolon is correct, though I’d have used a colon, which I think would be a bit more sophisticated in that sentence.”

The linguist Noam Chomsky sniffed, “I suppose Bush would claim it’s the effect of No Child Left Behind.”

New York City Transit’s unintended agenda notwithstanding, e-mail messages and text-messaging may jeopardize the last vestiges of semicolons. They still live on, though, in emoticons, those graphic emblems of our grins, grimaces and other facial expressions.

The semicolon, befittingly, symbolizes a wink.

This article has been revised to reflect the following correction:
Correction: February 19, 2008 An article in some editions on Monday about a New York City Transit employee’s deft use of the semicolon in a public service placard was less deft in its punctuation of the title of a book by Lynne Truss, who called the placard a “lovely example” of proper punctuation. The title of the book is “Eats, Shoots & Leaves” — not “Eats Shoots & Leaves.” (The subtitle of Ms. Truss’s book is “The Zero Tolerance Approach to Punctuation.”)