According to the Collins Dictionary, euthanasia is the practice of killing someone who is very ill and will never get better in order to end their suffering, usually done at their request or with their consent.

Euthanasia, also called mercy killing, act or practice of painlessly putting to death persons suffering from painful and incurable disease or incapacitating physical disorder or allowing them to die by withholding treatment or withdrawing artificial life-support measures. Because there is no specific provision for it in most legal systems, it is usually regarded as either suicide (if performed by the patient himself) or murder (if performed by another). Physicians may, however, lawfully decide not to prolong life in cases of extreme suffering, and they may administer drugs to relieve pain even if this shortens the patient’s life. In the late 20th century, several European countries had special provisions in their criminal codes for lenient sentencing and the consideration of extenuating circumstances in prosecutions for euthanasia.