Young children, defined as anyone under the age of about 50, might find this hard to believe, but there was a brief time when “groovy” was used without irony as a term of approbation.

“Feelin’ groovy” was a good way to feel.

This didn’t last, of course. They never do. Dating back at least to “cool” in the 1950s, there has always been some word that is shorthand for approval among younger people. (And one of the irritations of life is the discovery by every generation that however young you might feel — or actually be — someone else is younger.)

The life cycles of these words are generally similar, though always somewhat mysterious. They surface among teenagers, are adopted by their younger siblings and parents, spread to the adult population generally and end up in television commercials for mundane products, at which point they are no longer suitable for use by teenagers because they are uncool.

We at Bloomberg View, as grown-ups, cannot state where things stand regarding “cool” and its descendants with the same certainty that we bring to less important issues such as the future of the euro. We can offer a few tentative theories.

The life span of these terms seems to be about three or four years.

Each one starts out with some degree of irony — if only that of exaggeration. Then it is used seriously for a while. Finally, the air quotes are welded on permanently, and the term becomes a joke.

“Cool” had a double run. First in the 1950s, when it was associated with jazz, which was coolness incarnate. Then it had another good run in the 1990s or so, when the irony came from the fact that it was such an antiquated term.

At the turn of the century, there was “hot” — prized for the humor of its meaning roughly the same thing as “cool,” and for its sexual overtones.

The most obviously ironic term was “bad” — meaning good, a usage popularized by blacks in the late 1960s and 1970s. Its appeal was partly the mock sense of speaking in code to fool the Man.

But the Man caught on soon enough. (He always does.) When college marching bands took up “Bad, Bad Leroy Brown” to play at halftime, it was definitely time to move on.

Other shorthand expressions of approbation during the last half of the 20th century included “boss,” “rad” (short, obviously, for “radical” and therefore not too interesting) and, of course, the embarrassing “groovy.”

As for the 21st century: The first decade or so was dominated by “awesome.”

Nothing was too mundane and too obviously not awesome to avoid this label. Have you picked up the dry cleaning? You have? Awesome. Is it raining today? Awesome. There’s a dead body in the middle of the living room. Awesome.

Obviously if everything is awesome, then nothing is truly awesome. But rather than hector you about remembering what is truly awesome — the smell of the dawn or the wonders of childhood or that sort of stuff — we will use the last dregs of your patience to tell you what’s next.

A preteen of our acquaintance said that among her friends, the one-word expression of approval is “sick.” At first we thought she was teasing us, but at least one parent has confirmed this. Another parent insisted that “sick” actually has been around for years.

Two crucial elements here are one-upmanship and secrecy. By definition, once grown-ups start to use a word, it is past its sell-by date. Any assertion on this subject (as opposed to any other subject) cannot be authoritative.

Nevertheless, we proceed and state that the word most likely to succeed in the tradition of “cool” is “perfect.” Once again, the joke lies in the inherent exaggeration.

Nothing is really perfect. But perfect it is, and all we can say is, “cool.”

Editorial by Bloomberg View