preemptive

Preemptive is an adjective describing actions or measures taken in anticipation of a possible threat, problem, or need, with the aim of preventing or mitigating it before it arises. The term derives from Latin praemptus, meaning "taken before," from praemere "to buy or take beforehand."

In military and international relations, a preemptive strike or preemptive war is a use of force intended to neutralize an imminent threat before it can materialize. This is distinct from preventive war, which seeks to counter a potential threat that is not believed to be imminent. International law debates the legality and ethics of preemption and anticipatory self-defense.

In business and law, preemptive rights allow existing shareholders to purchase new shares before others, helping maintain proportional ownership. The term also appears in other contexts where authorities act early to forestall potential issues.

In computer science, preemptive scheduling is a CPU scheduling approach that can interrupt a running process to switch to a higher-priority task. In contrast, non-preemptive scheduling lets the current task run until it finishes or yields. In medicine, preemptive analgesia refers to interventions designed to prevent postoperative pain by treating it before it starts.