Euthanasia is the act or practice of ending the life of an individual suffering from a terminal illness or an incurable condition, as by lethal injection or the suspension of extraordinary medical treatment.
Various definitions and terminology
Voluntary euthanasia -- When the person who is killed has requested to be killed.
Non-voluntary euthanasia -- When the person who is killed made no request and gave no consent.
Involuntary euthanasia -- When the person who is killed made an expressed wish to the contrary.
Assisted suicide -- Someone provides an individual with the information, guidance, and means to take his or her own life with the intention that they will be used for this purpose. When it is a doctor who helps another person to kill themselves it is called "physician assisted suicide."
- Euthanasia (PDF), by Keith H. Essex