All over the world most people believe health to be just the absence of disease. But, like most other human concepts, the meaning of health has evolved over time. Initially health was seen as merely the absence of disease. But in 1948, the World Health Organization defined health as a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity. This definition has brought to light the concept of well-being in terms of physical well-being, mental well-being, and social well-being.