The other night in my favorite bar a woman cornered me with a long rant about how people are letting English go to the dogs. Too much slang, apparently. One hears this a lot, but it’s easy to miss that today’s slang can become tomorrow’s grammar. Exactly this is happening under our noses among young brown folks.

I speak of yo. Time was that yo was used as in “Yo! Get off of there!” But nowadays, yo has floated to the ends of sentences and lost its shouting intonation. Listen to young black men, in particular, talking casually and you hear sentences like “The party was really off the hook, yo.”

This is a brand new yo. The pronunciation here is not ” … hook, Yo!” The “hook, yo” in that sentence is pronounced with the same melody as on ice cream. The new yo has no accent. It has become what linguists call a pragmatic marker.

Asked what this usage of yo means, even people who use it draw a blank, just as we all would if asked what “even” means in, “The senator didn’t even show up.” “Even” does not have meaning in this usage; it serves a function — indicating that you find what you are referring to is unexpected or inappropriate.

In the same way, the new “yo” is no longer an interjection. It serves a function, just as even does — in the case of “yo,” the function is soliciting the empathy of the listener.

Interestingly, this “yo” makes Black English more like Chinese than standard English. In Cantonese, instead of “yo” there is “lo,” which has the same feel and function. If you say “Ngoh gokdak keuih m-ngaam lo,” it means roughly, “He’s not playing fair, yo.”

There are little words like this with this function in countless languages around the world. As spoken among America’s young and brown, English has joined them. An English with what linguists would call a persuasive pragmatic particle is more complex in that regard than Standard English. However, because nonstandard speech is perceived as “wrong,” Standard English will never have a persuasive pragmatic particle like Cantonese does. In fact, “yo” is not the first time English has reached for pragmatic complexity and been shot down by people like the woman I was talking to at the bar.

In the marvelous old comic strip, “Krazy Kat,” George Herriman had his characters speaking in a stylized amalgam of highfalutin, Ellis Island, and New York bridge-andtunnel. Ignatz Mouse, or “Ignatz Mice” as Krazy called him, leaned towards the latter.

Now and then, amidst Ignatz’ Jackie Gleason-esque speech style, he would come up with something like: “Hmm — so he was trifling with me, hey?”

Now, that “hey” initially seems a little clumsy. Try saying that line out loud. We imagine “hmm” or “ay” rather than “hey.” The “hey” seems simply unnatural, neither elegant, nor “Yiddische,” nor slangy, but just odd.

One encounters that use of hey in various stone-age American comic strips and vaguely senses that, for example, the artists back then just didn’t quite know how to write realistic dialogue. But Herriman’s attention to verbal nuance elsewhere makes it unlikely that these “heys” were just evidence of a tin ear for real talk.

There is, in fact, recorded evidence that Herriman and the others were getting something real down in print. Before “I Love Lucy,” Lucille Ball starred in a radio sitcom, “My Favorite Husband,” which was in retrospect a kind of dress rehearsal for the television show that would take the nation by storm. Already she was the daffy wife always giving her hubby trouble, including donning costumes and playing parts.

In one episode in the late forties, Lucy has to pose as a gum-popping gal from Brooklyn. Her characterization includes postposing “hey” to every second sentence: “Why don’t we meet down at the station, hey?” and “It was the only way I could find it, hey.” Again, the “hey” has no accent. It wasn’t “Down at the station — hey!” Instead, ” … station, hey” had the melody of overcoat.

Between Ignatz and Lucy, then, we see that in America before about 1950, vernacular speech in at least New York included a use of “hey” as a pragmatic marker just like the “yo” baggy-pants teens are using today. Thus the “yo” that the woman would dismiss as slang is in fact something that adds to the grammatical apparatus of the language. It makes English more like, say, Japanese, where a little word “ne” is used in the exact same way.

In Japanese you can even use it alone and ask someone “Ne?” which means, basically, “Are you okay? Is everything all right?” And no one calls it slang, hey.

Mr. McWhorter is a senior fellow at the Manhattan Institute.