Really.

Really?

No: Just . . . Really.

Ah! REALLY!

No. Just "Really." Like "for sure." That kind of "really." Like somebody says "War is hell," or "You can't fight city hall," and you say "really." Very flat, fatalistic, passive. Really.

You do not say it, however, if you want your speech to glitter with the latest syntactical sequins: "Really" has been dumped already into the Goodwill bin of slang by the nattier of our street semanticists. Now they say "for sure."

Understand?

If so, say: "I hear you." If glad of the information, express thanks "for sharing it with me."

If, however, you fear you've been outshone and superseded, wait until your conversational partner takes a stand you agree with, such as: "It gets so tired when people come back from California talking about sharing their personal space."

Even though you mean to reply by saying "really" or "for sure" or "I hear you," don't. Instead, merely say: "Thank you."

It's a question of social survival, and a basic function which prudery, denier of basic functions, has kept us from talking about. We all like to think that our speech arises from some immutable personal essence, as natural as a good backhand. Consequently, we savage each other at every opportunity for lapses of authenticity.

For instance: 'A lot of people come through California and go to a couple of workshops in the human potential movement. They hear this language and think it's a cool thing to do," complains a Berkeley professor of linguistics who claims that Californians have "extended the language to talk about emotions."

Really.

Garry Trudeau, creator of the comic strip "Doonesbury," has been mocking if lately as "mellowspeak" - the word "mellow" being yet another concept/buzzword of our times. (The word "buzzword," of course being jargon among some jargon-users, such as management consultants, for, well, jargon.)

Cyra MacFadden, author of "The Serial," a novel which satirizes life in a San Francisco suburb, calls it psychobabble." And linguists might call it the argot of a subculture; and the recent proliferation of purists (New-man, Safire, Simon & Co.) would rage against it the way they attack punctuators such as "y'know," which, in any case, has been replaced, okay, by the use of the word "okay."

For sure. Or, among the hip black community: "No question."

Julian Boyd, of Berkeley's English department, refers to the really/y'know/I-hear-you constellation as "modals," by which he means "words like 'maybe,' 'possibly,' 'hopefully' - words that have to do with truth being expressed. And they're always shifting. Once there was a difference between 'may' and 'might,' for instance, 'might' being less certain than 'may.'

" 'I hear you' is definitely new, though I think it's changing to 'I'm hearing you.' now. It's a nice ploy, when you think about it. It means that I can understand how you feel, but I don't necessarily endorse it."

"Really," in its new pronunciation, does the same, expunging the amazement or disgust implied in the old usage, to denote a commonality of experience, which is to say a space that's been shared.

Also, despite California's claims, these locutions are means of avoiding commitment and intimacy in the name of permissiveness.

But all of this misses the point. The point is not subcultures, linguistics, the human potential movement or even California, which, in itself, has become a word which is replacing "uptown" as a word meaning competitively fashionable.

Okay. Thank you.

The point is fashion. The fact that we're deriving our latest wardrobe of slang from psychological cultists in California means no more - and no less - than, say, Ralph Lauren being inspired by cowboys for his latest line of men's wear.

"It's so imprecise," says Georgetown University's Philip Herzbrun, who worked with H. L. Mencken on his last edition of "The American Language."

"It's largely to communicate attitued, rather than concept or fact. It doesn't have to be informal to do it, either - what we call standard English is a class dialect of about 20 percent of Americans. It identifies them to each other."

Says Ray Brown, chairman of Bowling Green University's popular culture department, "A lot of people worry about slang, but that's a mistake. It gives the language its vitality."

And despite all our carping, the semantic fashion show continues with new slang terms prowling down the runway like Calvin Klein models, The New Sound, dress it up, dress it down.

Dress it up, for instance, with a revival of interest in U (upper-class) and Non-U words curtains and drapes, rich and wealthy, dinnerjacket and tuxedo, for instance.

Dress it down with citizen's band-radio talk: 10-4, good buddy. That veers into the redneck chic which brought words such as "hassle" to the hippies, who revived beatnik usage of "far out" and dipped into black slang for "right on" and "get it on." For a whole "get" series, in fact: get down (shed inhibitions and boogie), and a more recent black-to-white crossover, "get over," meaning succeed or persuade, usually with illicit overtones, as in "Look at that dude trying to get over on that sweet lady." "Lady" being what we say now that we don't have to say the feminist-certified "woman," which replaced "girl."

Just as we've had retro-fashion in clothes, deliberately anachronistic styles, we keep going back to old slang for a new look. The '30s and '40s term for women's legs, for instance: gams. It dates back at least to the 18th century, says the University of Chicago's Raven McDavid.

To be fashionable, however, retro-slang must be musty enough to be conspicuously self-conscious. "Groovy," for instance, has so recently left hip usage that it merely provokes embarrassment. But Washington photographer Allen Appel has for years been sprucing up dreary art-world chatter about callous curators with his '50s hipster argot, whenever you fall by his pad. Solid.

In Los Angeles, Wet, the magazine of "gourmet bathing," favors '50s mainstream slang, such as "Look at David in his sharp new clothes." Wet, be warned, is the leading oracle of the L.A. zeitgeist. As Allen Ginsberg once said: "Who loves Los Angeles is Los Angeles."

None of this is to be confused with the collection of argot and occupational terms that attain notable but brief orbits outside the gravity of their origins - "boss," meaning good among surfers, "glitch" meaning mechanical failure among space technicians, "cop a sui," meaning to kill oneself, among the psychotherapized of New York's upper east side.

However, among the gay subculture, which is the AT&T of fad communication, current locutions include "the last" - meaning the ultimate, the best, an emotion also conveyed by saying that something is "to die for." And while once we aspired to be "cool," now it's "hot" (Just as "bad" once meant "good.")

And one recent visitor from Southern California reported that 14-year-olds out there, which is to say the Thought Police of American popular culture, are approving things not as boss, hot, neat, bad, or tough but - are you ready? - "gnarly."

Really. CAPTION: Illustration, no caption, By Dorothy Michele Novick fot the Washington Post