The term itself is a relic from the 1990s, the moment in which the ongoing crisis over North Korea’s nuclear ambitions began. At the end of the Cold War, the only nuclear weapons on the Korean Peninsula were American. The problem, from an American perspective, was that North Korea wanted to acquire nuclear weapons capabilities of its own. Ultimately, President George H.W. Bush’s administration chose to withdraw American nuclear weapons from South Korea as part of an effort to seek a diplomatic solution to the North’s nuclear ambitions. For a moment, it seemed like it would work: After the 1991 withdrawal of American nuclear weapons, South Korea and North Korea signed in 1992 a joint declaration on “the denuclearization of the Korean Peninsula.”

“Denuclearization” was conveniently abstract. That allowed it to capture different aspects of what James Baker, Mr. Bush’s secretary of state, called “the nuclear problem on the Korean Peninsula.” It covered at the same time the nuclear weapons that the United States withdrew from South Korea, the so-called “nuclear umbrella” of extended deterrence provided by the United States, and North Korea’s own nuclear weapons ambitions. It was a shapeless, ill-fitting word. But the alternatives — “disarmament” or “nonproliferation” — were just too narrow. Diplomats couldn’t squeeze everything that mattered into them.

Today, of course, things are very different than they were in 1992. There are no American nuclear weapons in South Korea (although the North Koreans don’t believe that, and some South Korean politicians have called for their return). More important, North Korea has moved in fits and starts to build a nuclear weapons capability that may be as large as 60 nuclear weapons, including a small number that can strike the United States.

But diplomats rarely throw phrases away, even once they are outdated. During the 2000s, “denuclearization” stuck around because the Joint Declaration was North Korea’s only written commitment to abandoning its nuclear weapons after Pyongyang withdrew from the Nuclear Nonproliferation Treaty in 2003. And so even as the situation has changed, many American policymakers have repurposed “denuclearization” as a synonym for North Korea’s disarmament.