Death is the termination of the biological functions that define a living organism. It refers both to a particular event and to the condition that results thereby. The true nature of the latter has, for millennia, been a central concern of the world's religious traditions and of philosophical enquiry. Belief in some kind of afterlife or rebirth is a central aspect of many religious traditions. Within the scientific community, many suppose death to terminate mind or consciousness. The effect of physical death on any possible mind or soul remains for many an open question. Cognitive science has yet to explain the origin and nature of consciousness; any view about the existence or non-existence of consciousness after death remains speculative.
Humans and the vast majority of other animals die in due course from senescence. Remarkable exceptions include the hydra, and the jellyfish Turritopsis nutricula, which is thought to possess in effect biological immortality.
Intervening phenomena which commonly bring about death earlier include malnutrition, disease, or accidents resulting in terminal physical injury. Predation is a cause of death for many species. Intentional human activity causing death includes suicide, homicide, and war. Roughly 150,000 people die each day across the globe. Death in the natural world can also occur as an indirect result of human activity: an increasing cause of species depletion in recent times has been destruction of ecosystems as a consequence of the widening spread of industrial technology.