A hospital is a very important institution. Hospitals are largery stuffed by professional physicians, surgeons, nurses and other health care stuff. Some patients go to a hospital just for diagnosis, treatment, or therapy and then leave hospital without staying overnight, while others stay overnight or for several days or weeks or even months, depending on the severity of the disorder. Hospitals allow to take care of the health of a large number of patients quickly and efficiently. If in modern cities were no hospitals, the average life expectancy of urban residents would be much less.