Caregivers could shorten life to relieve pain. With this in mind, different types of euthanasia take on different shades of meaning. Medical professionals stop futile treatments and don't start alternate ones. The patient is allowed to die without intervention, letting nature take its course. Voluntary active euthanasia.
Someone kills a competent adult who requests assistance in dying.
Clinical depression, often occurring during advanced illness, doesn't automatically deprive the client of competence in these decisions. Nonvoluntary active euthanasia. This is considered homicide by law. Involuntary active euthanasia. A person doesn't seek the patient's opinion or the client requests to live, but kills anyway.