Death is the irreversible termination of the biological functions that define a living organism.
Death refers to both a particular event and to the condition that results thereby.
Many religions maintain a belief in either some kind of afterlife or rebirth.
The effect of physical death on any possible mind or soul remains for many an open question.
Within the scientific community, death is frequently associated with a belief in materialism and the complete ending of mind or consciousness.
consciousness itself has yet to be fully understood in science and psychology, and any view about the existence or non-existence of consciousness after death remains a speculative belief.
Animals almost without exception die in due course from senescence.
Intervening phenomena which commonly bring death earlier include malnutrition, predation, disease, accidents resulting in terminal physical injury, or, in extreme circumstances, grave ecosystem disruption. 
Malnutrition can be fatal.
Malnutrition can be a cause of death.
I could die of malnutrition.
People can die of malnutrition.
Disease can be fatal.
Disease can be a cause of death.
I could die of disease.
People can die of disease.
Many people die from diseases.
Accidents can be fatal.
Accidents can be a cause of death.
Intentional human activity causing death includes suicide, homicide, and war.
Suicide is an intentional human activity causing death.
Homicide is an intentional human activity causing death.
War is an intentional human activity causing death.
An intentional human activity that causes death is war.
An intentional human activity that causes death is suicide.
An intentional human activity that causes death is homicide.
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 ecological systems as a consequence of the widening spread of industrial technology.
Death is an important part of the process of natural selection.
Organisms that are less adapted to their current environment than others are more likely to die having produced fewer offspring, reducing their contribution to the gene pool of succeeding generations.
The genes of organisms are thus eventually bred out of a population, leading to processes such as speciation and extinction. It should be noted, however, that reproduction plays an equally important role in determining survival.
an organism that dies young but leaves many offspring will have a much greater Darwinian fitness than a long-lived organism which leaves only one.
Extinction is the cessation of existence of a species or group of taxa, reducing biodiversity.
Microorganisms also play a vital role, raising the temperature of the decomposing matter as they break it down into yet simpler molecules.
Not all materials need be decomposed fully, however. Coal, a fossil fuel formed over vast tracts of time in swamp ecosystems, is one example.
New varieties of organisms arise and thrive when they are able to find and exploit an ecological niche.
species become extinct when they are no longer able to survive in changing conditions or against superior competition.
Enquiry into the evolution of aging aims to explain why so many living things and the vast majority of animals weaken and die with age.
The evolutionary origin of senescence remains one of the fundamental puzzles of biology. Gerontology specializes in the science of human aging processes.
One of the challenges in defining death is in distinguishing it from life.
Death would seem to refer to either the moment at which life ends, or when the state that follows life begins.
determining when death has occurred requires drawing precise conceptual boundaries between life and death.
there is little consensus over how to define life.
Some have suggested defining life in terms of consciousness.
When consciousness ceases, a living organism can be said to have died.
Historically, attempts to define the exact moment of a human's death have been problematic.
Death was once defined as the cessation of heartbeat and of breathing, but the development of CPR and prompt defibrillation have rendered that definition inadequate because breathing and heartbeat can sometimes be restarted.
Events which were causally linked to death in the past no longer kill in all circumstances; without a functioning heart or lungs, life can sometimes be sustained with a combination of life support devices, organ transplants and artificial pacemakers.
Today, where a definition of the moment of death is required, doctors and coroners usually turn to "brain death" or "biological death" to define a person as being clinically dead; people are considered dead when the electrical activity in their brain ceases.
It is presumed that an end of electrical activity indicates the end of consciousness.
In order for death to occur, suspension of consciousness must be permanent, and not transient, as occurs during certain sleep stages, and especially a coma.
The possession of brain activities, or ability to resume brain activity, is a necessary condition to legal personhood in the United States.
Many have challenged the idea that brain death is equivalent to the cessation of consciousness.
Critics point out that much of human consciousness is embodied in numerous body parts and that the end of electrical impulses in the brain does not necessarily indicate that this embodied consciousness has also ceased.
brain death does not necessitate the end of consciousness, and thus brain dead people may still be alive.
even if brain death does mean the end of consciousness for a human being, the whole notion that cessation of consciousness indicates death is problematic.
Critics note the existence of many single-celled organisms such as bacteria that we consider to be alive but which many doubt are conscious.
If life does not require consciousness, defining death in terms of "brain death" is a dubious procedure, even if the brain is the seat of consciousness.
while legal concerns surrounding death force us to develop a working definition of death, it is not at all clear that the current American definition, according to brain death, coincides at all with a definition that can be reasonably endorsed.
Those people maintaining that only the neo-cortex of the brain is necessary for consciousness sometimes argue that only electrical activity there should be considered when defining death.
Eventually it is possible that the criterion for death will be the permanent and irreversible loss of cognitive function, as evidenced by the death of the cerebral cortex.
Even by whole-brain criteria, the determination of brain death can be complicated.
EEGs can detect spurious electrical impulses, while certain drugs, hypoglycemia, hypoxia, or hypothermia can suppress or even stop brain activity on a temporary basis. 
hospitals have protocols for determining brain death involving EEGs at widely separated intervals under defined conditions.
There are many anecdotal references to people being declared dead by physicians and then coming back to life, sometimes days later in their own coffin, or when embalming procedures are just about to begin.
In cases of electric shock, CPR for an hour or longer can allow stunned nerves to recover, allowing an apparently dead person to survive.
People found unconscious under icy water may survive if their faces are kept continuously cold until they arrive at an emergency room.
As medical technologies advance, ideas about when death occurs may have to be re-evaluated in light of the ability to restore a person to vitality after longer periods of apparent death.
The lack of electrical brain activity may not be enough to consider someone scientifically dead.
By law, a person is dead if a Statement of Death or Death Certificate is approved by a licensed medical practitioner.
Various legal consequences follow death, including the removal from the person of what in legal terminology is called personhood.
The leading cause of death in developing countries is infectious disease.
The leading causes of death in developed countries are atherosclerosis, cancer, and other diseases related to obesity and aging.
The leading causes of death in developed countries are heart disease and stroke, cancer, and other diseases related to obesity and aging.
Of the roughly 150,000 people who die each day across the globe, about two thirds or 100,000 per day, die of age-related causes.
With improved medical capability, dying has become a condition to be managed.
Home deaths, once normal, are now rare in the developed world.
In developing nations, inferior sanitary conditions and lack of access to modern medical technology makes death from infectious diseases more common than in developed countries.
Malaria causes about 400–900 million cases of fever and approximately one to three million deaths annually.
tuberculosis is a bacterial disease which killed 1.7 million people in 2004.
AIDS death toll in Africa may reach 90-100 million by 2025.
mortality due to malnutrition accounted for 58% of the total mortality rate in 2006.
worldwide approximately 62 million people died from all causes and of those deaths more than 36 million died of hunger or diseases due to deficiencies in micronutrients.
Tobacco smoking killed 100 million people worldwide in the 20th century and could kill 1 billion people around the world in the 21st century.
Many leading developed world causes of death can be postponed by diet and physical activity, but the accelerating incidence of disease with age still imposes limits on human longevity.
The evolutionary cause of aging is, at best, only just beginning to be understood.
It has been suggested that direct intervention in the aging process may now be the most effective intervention against major causes of death.
Signs of death, or strong indications that a person is no longer alive are: Ceasing respiration, pallor mortis, livor mortis, algor mortis, rigor mortis, and decomposition.
Ceasing respiration is a symptom of death.
Pallor mortis is a symptom of death.
Livor mortis is a symptom of death.
Algor mortis is a symptom of death.
Rigor mortis is a symptom of death.
Decomposition is a symptom of death.
Pallor mortis is paleness which happens almost instantaneously.
Pallor mortis is paleness which happens in the 15–120 minutes after the death.
Livor mortis is a settling of the blood in the lower portion of the body.
Algor mortis is the reduction in body temperature following death.
Rigor mortis is when the limbs of the corpse become stiff and difficult to move or manipulate.
Decomposition is the reduction into simpler forms of matter.
A symptom of death is a sign of death.
A sign of death is the same as a symptom of death.
An autopsy is a medical procedure that consists of a thorough examination of a human corpse to determine the cause and manner of a person's death and to evaluate any disease or injury that may be present.
An autopsy is also known as a postmortem examination.
Autopsies are either performed for legal or medical purposes.
A forensic autopsy is carried out when the cause of death may be a criminal matter, while a clinical or academic autopsy is performed to find the medical cause of death and is used in cases of unknown or uncertain death, or for research purposes.
Autopsies can be further classified into cases where external examination suffices, and those where the body is dissected and an internal examination is conducted.
Permission from next of kin may be required for internal autopsy in some cases.
Once an internal autopsy is complete the body is generally reconstituted by sewing it back together.
Autopsy is important in a medical environment and may shed light on mistakes and help improve practices.
A "necropsy" is an older term for a postmortem examination, unregulated, and not always a medical procedure.
Life extension refers to an increase in maximum or average lifespan, especially in humans, by slowing down or reversing the processes of aging.
Average lifespan is determined by vulnerability to accidents and age or lifestyle-related afflictions such as cancer, or cardiovascular disease.
Extension of average lifespan can be achieved by good diet, exercise and avoidance of hazards such as smoking.
Maximum lifespan is determined by the rate of aging for a species inherent in its genes.
Currently, the only widely recognized method of extending maximum lifespan is calorie restriction. 
Theoretically, extension of maximum lifespan can be achieved by reducing the rate of aging damage, by periodic replacement of damaged tissues, or by molecular repair or rejuvenation of deteriorated cells and tissues.
Researchers of life extension are a subclass of biogerontologists known as "biomedical gerontologists".
Researchers of life extension try to understand the nature of aging and they develop treatments to reverse aging processes or to at least slow them down, for the improvement of health and the maintenance of youthful vigor at every stage of life.
Those who take advantage of life extension findings and seek to apply them upon themselves are called "life extensionists" or "longevists". 
The primary life extension strategy currently is to apply available anti-aging methods in the hope of living long enough to benefit from a complete cure to aging once it is developed, which given the rapidly advancing state of biogenetic and general medical technology, could conceivably occur within the lifetimes of people living today.
Death is the center of many traditions and organizations, and is a feature of every culture around the world.
Legal aspects of death are also part of many cultures, particularly the settlement of the deceased estate and the issues of inheritance and in some countries, inheritance taxation.
Capital punishment is also a divisive aspect of death in culture.
In most places that practice capital punishment today, the death penalty is reserved as punishment for premeditated murder, espionage, treason, or as part of military justice.
In some countries, sexual crimes, such as adultery and sodomy, carry the death penalty, as do religious crimes such as apostasy, the formal renunciation of one's religion.

In many retentionist countries, drug trafficking is also a capital offense.
In China human trafficking and serious cases of corruption are also punished by the death penalty.
In militaries around the world courts-martial have imposed death sentences for offenses such as cowardice, desertion, insubordination, and mutiny.
Death in warfare and in suicide attack also have cultural links, and the ideas of dulce et decorum est pro patria mori, mutiny punishable by death, grieving relatives of dead soldiers and death notification are embedded in many cultures.
Recently in the western world, with the supposed increase in terrorism following the September 11 attacks, but also further back in time with suicide bombings, kamikaze missions in World War II and suicide missions in a host of other conflicts in history, death for a cause by way of suicide attack, and martyrdom have had significant cultural impacts.
Suicide in general, and particularly euthanasia are also points of cultural debate.
Death is personified in many cultures, with such symbolic representations as the Grim Reaper, Azrael and Father Time.