Source:http://linkedlifedata.com/resource/umls/id/C0015187
MSH: The act or practice of killing or allowing death from natural causes, for reasons of mercy, i.e., in order to release a person from incurable disease, intolerable suffering, or undignified death. (from Beauchamp and Walters, Contemporary Issues in Bioethics, 5th ed),NCI: An easy or painless death, or the intentional ending of the life of a person suffering from an incurable or painful disease at his or her request.