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.
watershed waÂ·terÂ·shed (wÃ´'tÉr-shÄd') n. A ridge between two areas that directs drainage to either side. The area of marginal blood flow at the extreme periphery of a vascular bed.