By definition, what is a nuclear weapon?

A nuclear weapon is fundamentally a complete assembly designed to produce an intended nuclear reaction that results in the rapid release of a vast amount of energy. This definition encompasses not only the physical device but also the specific mechanisms that allow it to achieve a nuclear chain reaction, whether through fission, fusion, or a combination of both.

This comprehensive definition clarifies that a nuclear weapon is not merely a device that creates an explosion, which could apply to conventional explosives as well. It distinguishes itself as a system engineered to trigger a significant nuclear reaction, which leads to the enormous energy output characteristic of nuclear weapons. This understanding is crucial in recognizing what constitutes a nuclear weapon beyond just the immediate violent effects or the presence of radioactive materials.