Death due to disease is called death by natural causes. There are four main types of disease: pathogenic disease, deficiency disease, hereditary disease, and physiological disease. Diseases can also be classified as communicable and non-communicable disease.
A watershed is the area of land where all of the water that falls in it and drains off of it goes to a common outlet.
In North America, the term watershed is commonly used to mean a drainage basin, though in other English-speaking countries, it is used only in its original sense, to mean a drainage divide, the former meaning an area, the latter the high elevation perimeter of that area.ach drainage basin is separated topographically from adjacent basins by a perimeter, the drainage divide making up a succession of higher geographical features (such as a ridge, hill or mountains) forming a barrier.