A friend of mine, a man who chases the cutting edge of change the way his Gallic ancestors once pursued the Holy Grail, tells me that he is now "post-Yuppie." This isn't a formal announcement, mind you. That isn't necessary.

I already knew that Yuppiedom was pass,e. In selected urban areas, women have burned their bow ties, begun leaving their running shoes at home and grown defensive about ordering white-wine spritzers. Men are increasingly secretive about owning VCRs and embarrassed to have the espresso machine right out there on the kitchen counter.

It was inevitable that my friend, who along with two others is probably a member of the reigning troika of trends (I suspect they have a New York magazine reporter permanently assigned), would be early in and early out of Yuppiedom.

So what struck me was not the fact that he was in a post-Yuppie phase. It was the fact that he was using a post- Yuppie phrase.

With nary a warning from the traditional trend spotters, it appears that the post-war babies of the post-industrial society have begun placing their favorite prefix all over the American scene. These are the four little letters -- -p,o,s,t -- which once meant "after," as in post-operative. But now they are being used to write premature political post-mortems.

Consider the academic who recently drew a profile of middle-class young American voters. They were, he told a reporter, "post-ideological."

The implication was that these voters had already been through the heavy philosophical stuff. They were not hostile to ideology, they were beyond it. Perhaps they'd taken it freshman year. Now, ideology was a bit like a Betamax. It was okay, but they wouldn't want to get stuck with it when something better came along.

Last year, the big phrase was post- feminist. Any young woman who had not personally signed up for Radical Feminist Cell 16 was called a member of the post-feminist generation. The label managed to weardate the women's movement so that it seemed unfashionable. Feminism itself was described as something the country had outgrown.

Putting the four-letter "post" before the right sort of word is the kiss of datedness. The word becomes a Perrier gone flat in the marketplace. But it does this in the most apparently benign, nonjudgmental, neutral sort of way.

Consider the man I heard on the radio talking about the needs of Americans in the post-civil-rights era. The what? Separation of church and state, and free speech, he went on flatly, were all splendid ideas, but well, what do we need now, for the 1980s?

Then there are the commentators who talk about the Reagan post-welfare state, instead of what they mean: the anti-welfare state. There are even sociologists talking calmly about a post-literate world and a post-verbal generation. Once a 35-year-old described himself to me as a post-peacenik. I did not at that moment have the nerve to ask him whether he currently was "into" war.

I suppose there might be some modest value in this post-age. I think it would be amusing to be post-young instead of middle-aged. Reformed smokers could become post-smokers. Atheists could choose to be post- theists. Vegetarians could be post-carnivores. Retired citizens, post-workers. Divorce, post-marriage. The rest I would leave to post-erity.

But I am wary of linguistic tricks. "Post" is being sprinkled through the political language more generously than the dreaded "neo" ever was.

If my friend wants to be post- Yuppie, good luck to him. In his trendy troika the Yuppie has gone the way of the Babbitt and the Preppie. I don't care if he stops serving shitake mushrooms the way he once quit on kiwis. There is hardly any social judgment to be made between shitakes and chanterelles. No one really cares if we live in a post-kiwi world (except, I suppose, the kiwi grower).

But I get uncomfortable when we turn ideas into trends, when we trivialize concepts and values into games of "ins" and "outs." When ideology, literacy and civil rights are treated like racquetball, nouvelle cuisine and new- wave music, it's time to write a post- script to the era: label it post-cerebral.