Euthanasia
If you take 15-year-old Fido to the vet to put him down before the dog diabetes gets any worse, you probably won't have any problems. But if you try to do the same for your terminally ill 83-year-old grandma you're bound to encounter a few raised eyebrows--not to mention you'd probably get arrested.

When you actively assist an ill person in committing suicide--say, by deliberately feeding them an overdose of painkillers--you're performing an act of euthanasia. Individuals who are euthanized typically have some type of sickness that will soon kill them. Unlike animals it is their decision to be euthanized, and they usually request help in ending their life from someone they trust.

Assisted suicide is different from euthanasia in that you provide the terminal person with the means to kill themselves only (but don't actually perform the act yourself).

Both euthanasia and assisted suicide are legal only in Oregon, the Netherlands and Belgium. But as the case of Dr. Kevorkian (a Michigan doctor convicted for second-degree murder for assisting in the suicides of several patients) and several overturned laws permitting euthanasia suggest, the issue is far from decided.