What is Disease,? It is any deviation from or interruption of the normal structure or function of any body part, organ, system (Systems) that is manifisted by a characteristic set of symptoms and signs for which the pathology,etiology,prognosis, may be known or unknown. This its really sound weird,but its true. Let us speak about this in very simple way with no medical terms. If your body temprature start rising with chills and shivering then it is called fever. This rising of body temprature is a positive feedback mechanism of your body. Fever is our friend,because your body can tolerate it upto a certain level, but beyond that it is critical and it becomes difficult for the body to tolarate it. Without pathology etiology etc doctors are sometimes not able to find the exact cause of disease. So it best to keep ourselves free from disease by keeping ourselves mentally and physically fit.