Definitions of pain in all disciplines associate pain with unpleasantness. Physiology links pain with unpleasantness to make humans aware of imbalances in the body. Biology links pain and discomfort as an evolutionary tool. Humans avoid discomfort/pain and this keeps them alive. Psychology associates pain with unpleasantness of the mind. Pain is described by all disciples as a subjective experience, which can only be explained by those who experience it. Pain is related to the disease of the “body”, from the point of view of the physiologist, or of the “mind” from the point of view of the psychologist.