The recruiter was pleased that the law firm was interested in one of his clients. “I will revert with candidate details soon,” he wrote in an e-mail to the firm’s hiring manager.

Gee, if he wanted his client to get a job, why would he “revert” anything? After all, “revert” means “turn back,” or “return to its original state,” or something of that ilk, right?

Turns out we are witnessing the etymological equivalent of a volcanic eruption; the “reversion,” if you will, of molten rock back into solid rock. And, as is the case with lava, the new shape is not the same as the old, though it’s made of the same stuff.

“Revert” already has nearly a dozen definitions in the Oxford English Dictionary, our best guide to the primordial soup that is our language, all of them having at their base the idea of a “return”—to health, of land, to an idea, to a previous state, etc. One of them is not—yet—to “reply,” which is how the recruiter used “revert.” But one of the “legitimate” definitions is “to return to a topic of discussion.” What is “to reply” but “to return to a topic of discussion”?

It does not take much for such a small evolutionary change to take place, but it does take some time before it is recognized as a legitimate species, not merely a hybrid. (One definition of “revert,” by the way, is biological, “to go back to an earlier, former, or primitive type.”)

In a 2010 “On Language” column, Ben Zimmer noted this usage and said, “It turns out that unbeknownst to most dictionaries, revert has been leading another life in several varieties of world English, notably the kind spoken on the Indian subcontinent.” It also seems to have surfaced in other areas where British usage prevails, such as the Caribbean, Hong Kong, and Shanghai, though not, apparently, in England itself. Urbandictionary.com, that least Darwinian of etymological chroniclers, says that using “revert” to mean “to reply” is “Indian English.” A management company even includes “revert” in its guide to doing business in the subcontinent. Young people are more prone to use it than the Neanderthals over thirty-five.

But this new piece of land is still too hot to walk on if you’re writing for American publications (and probably if you’re looking to place lawyers, too), and it will probably be years before you click “revert all” on an e-mail message, if ever. While few people would misunderstand if you used “revert” instead of “reply,” most would probably believe you had engaged in a malapropism, and think less of you for it.

There’s one more hot spot in “revert,” and it has nothing to do with “replying.” Because any definition of “revert” has buried within it the sense of a “return,” accompanying “revert” with “back” is just plain redundant. Let that usage sink back into the earth.

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Merrill Perlman managed copy desks across the newsroom at The New York Times, where she worked for 25 years. Follow her on Twitter at @meperl.