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.
A watershed is an area of land in which all of the water that enters it, drains into a common waterbody. Also known as a drainage basin, it can be thought of as a funnel that collects surface water and ground water and drains it into a single stream, lake, ocean, or other reservoir.