The conflict hinged on a single word: “gravy.”

The place was Heathrow Airport, the time the mid-1970s. The airport had recently hired a group of Indian and Pakistani women to work in its employee cafeteria, and trouble had arisen between them and the British baggage handlers they served.

The baggage handlers complained that the servers were rude, and the servers complained that the baggage handlers were discriminating against them. Neither group knew why the other felt the way it did.

Enter John J. Gumperz. Professor Gumperz, a linguist at the University of California, Berkeley, who died on Friday at 91, was one of the leading authorities on discourse analysis, which studies not only who says what to whom, but also how it is said and in what context.

At the time of the Heathrow incident, he was on sabbatical in England and was called in to help.

Professor Gumperz, who at his death was an emeritus professor in Berkeley’s anthropology department, was a sociolinguist, whose field stands at the nexus of linguistics, anthropology and sociology. But though sociolinguistics as a whole embraces spoken language and the printed word, he concentrated on face-to-face verbal exchanges.