In ancient Greek, the term euthanatos meant "easy death". Today euthanasia () generally refers to mercy killing, the voluntary (自愿) ending of the life of someone who is terminally ill. Like abortion, euthanasia has become a legal, medical, and moral issue over which opinion is divided. Euthanasia can be either active or passive. Active euthanasia means that a physician or other medical personnel takes an action that will result in death, such as giving an overdose of deadly medicine. Passive euthanasia means letting a patient die for lack of treatment, or stopping the treatment that has begun. Examples of passive euthanasia include taking patients off a breathing machine or removing other life-support systems. Stopping the food supply is also considered passive. A good deal of the debate about mercy killing originates from the decision- process. Who decides whether a patient is to die This issue has not been solved legally in the United States. The matter is left to state law, which usually allows the physician in charge to suggest the option of death to a patient’’s relatives, especially if the patient is brain dead. In an attempt to make decisions about when their own lives should end, several terminally ill patients in the early 1990s used a controversial suicide device, developed by Dr. Jack Kevorkian, to end their lives. In parts of Europe, the decision- process has become very flexible. Even in cases where the patients are not brain dead, patients have been put to death without their approval at the request of relatives or at the suggestion of physicians. Many cases of passive euthanasia involve old people or newborn infants. The principle justifying this practice is that such individuals have a "life not worthy of life". In countries where passive euthanasia is not legal, the court systems have proved very tolerant in dealing with medical personnel who practice it. In Japan, for example, if physicians follow certain guidelines they may actively carry out mercy killings on hopelessly ill people. Courts have also been somewhat tolerant of friends or relatives who have assisted terminally ill patients to die. The difference between active and passive euthanasia is whether______.