Nonproliferation Treaty (NPT): An international treaty whose objective is to prevent the spread of nuclear weapons and weapons technology, to promote peaceful uses of nuclear energy (such as electricity production) and encourage disarmament. 190 nations are party to the NPT. Notable holdouts are India, Israel, North Korea, and Pakistan – four of the nine states that possess nuclear weapons.
Nuclear-weapon state: States that legally (under the NPT) possess nuclear weapons. These nations are the United States, the United Kingdom, France, China, and Russia. They all tested nuclear devices prior to January 1, 1967 and thus were allowed to maintain their weapons per the NPT.
International Atomic Energy Agency (IAEA): An international organization whose aim is to promote peaceful use of nuclear energy and to inhibit its use for military purposes such as radiological and nuclear weapons.
Intermediate-Range Nuclear Forces Treaty (INF): An arms control treaty between the United States and the Soviet Union that entered into force on June 1, 1988. It banned all land-based ballistic and cruise missiles with ranges 500-5,500 km (310-3,420 miles), which are considered short to intermediate range. President Donald Trump withdrew from the INF in October 2018; the next day, Russia followed suit.
A.Q. Khan: A Pakistani nuclear physicist and engineer who founded the uranium enrichment program for Pakistan’s atomic bomb development. The “A.Q. Khan Network” was a black market of nuclear technology, started in the 1970s, that was used in the proliferation of Iran, Libya, and North Korea.
Dual-Use Technology: Products and technologies that have both civilian and military uses. A common example would be chlorine. Chlorine is oft used to purify water but may also be used to build chemical weapons. As such, trade in dual-use products are regulated.
Sanctions: Economic sanctions are commercial and financial penalties applied by individual or blocs of states (e.g. United Nations, European Union) against a targeted state. These sanctions include various forms of trade restrictions, barriers, and tariffs. Information on international sanctions against North Korea can be read here, from the Council on Foreign Relations.
Nuclear Suppliers Group: A multilateral export control regime whose aim is to prevent proliferation by controlling the trade of materials, equipment, and technology that can be used to build nuclear weapons.
Sagan-Waltz Debate: A fundamental debate in the study of nuclear policy and nonproliferation regarding the utility and security of nuclear weapons proliferation. To grossly simplify the arguments: Sagan says if no one had nuclear weapons, then no one could use them. Waltz says if everyone had nuclear weapons, then no one would use them.