Euthanasia, often referred to as "mercy killing", "means any action committed or omitted for the purpose of causing or hastening the death of a human being after birth, allegedly for the purpose of ending the person's suffering."
There are different types of euthanasia/assisted suicide:
Passive (negative, indirect) euthanasia is action withheld for the purpose of causing or hastening death. These measures include the withholding or withdrawal of non-heroic measures, including food, hydration (water), and oxygenation. An example of passive euthanasia is the withholding of food and water from a person in a so-called "persistent vegetative state," or from someone whose health is not improving rapidly enough in the opinions of the attending health care workers. Note that the term "indirect," when applied to a euthanasia case, has a different meaning than when applied to "double effect" cases of abortion and sterilization.
Voluntary euthanasia is committed with the willing and autonomous cooperation of the subject. This means that the subject is free from direct or indirect pressure from others.
Involuntary euthanasia is committed without the knowledge and/or consent of the subject. Permission may be granted by a court or by family members, or at the discretion of the attending health care professional or caretaker.
Assisted suicide is the act of providing means in order to help a person take his or her own life. Physician-assisted suicide simply means that a doctor provides the means for a person to end their life. Specifically, this means that the physician provides a prescription or other means for a person to commit suicide; the patient, not the doctor, actually performs the lethal act. It is important to be clear as to which medically-based decisions at the end of life should not be classified as euthanasia. Both active and passive euthanasia involve the intention to end a life. Allowing a terminally-ill person in the last stages of life to die a natural death is not euthanasia. Where the situation is medically hopeless, a decision not to provide or continue extraordinary or heroic measures—where such no longer offer any hope for healing—is ethical, legal and consistent with standard medical practice.