Euthanasia, (from
Greek: åõèáíáóßá -åõ, eu, "good", èÜíáôïò, thanatos,
death),is the practice of terminating the life of a person or animal in a painless or minimally painful way in order to
stop suffering or other undesired conditions in life.
So in fact it's just ending someone's misery.
The man could have lived for another month, but the cancer had gone too
far. They performed euthanasia to end his life withoug further
pain.