“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. …

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.”

-Sam Roberts, "Celebrating the Semicolon in a Most Unlikely Location," New York Times