kill

Kill is a verb meaning to cause the death of a living being. It can refer to an intentional act, an accidental death, or death caused by natural processes. The term originates in Old English cwellan, with cognates in other Germanic languages, and it has entered many specialized fields with distinct meanings.

In legal and ethical discussions, killing a person is typically described as homicide; classification depends on intent and circumstances. Murder denotes unlawful killing with malice aforethought, while manslaughter covers killings without premeditation or with mitigating factors. Justifiable homicide includes self-defense or defense of others under certain conditions. Laws vary by jurisdiction but share the aim of distinguishing culpability and justifiable conduct.

In biology and medicine, death can be natural or regulated. Programmed cell death (apoptosis) is an active, controlled process important for development and homeostasis, whereas necrosis refers to uncontrolled cell death from injury. In microbiology and pharmacology, agents that kill microorganisms are described as bactericidal, fungicidal, or virucidal; disinfectants and sterilants are evaluated by their killing efficacy. In technology, kill is used to describe terminating processes; the Unix command kill sends signals to a program to stop, typically using signals such as SIGTERM or SIGKILL.

In culture, the word appears in many titles and expressions and is used metaphorically to convey destruction or the end of life in discussions of ethics, war, and crime. The term thus spans practical, legal, scientific, and figurative domains.