Death
When people talk about things or events that lead to the death of a plant or animal, those things or events are usually described as being deadly, or fatal. In the case of diseases, they are described as 'terminal'. Humans are no different from any other lifeform. Our bodies have an ability for self-repair, but that ability is limited. Finding the cause of death is a medical speciality called pathology. In medicine, death is when the heart stops beating for more than several minutes. There are special times in which people recover even though the heart has stopped for 30 minutes, such as near-drowning in very cold water. If machines are used to help the heart and lungs work, then the moment of death is more difficult to know.