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 the area of land where all of the water that is under it or drains off of it goes into the same place (generally a creek or river). As you might imagine a watershed can be many different sizes. They cross county, state, and national boundaries, and no matter where you are, you're in a watershed! For example, here in Northampton County, we all live in the Delaware River Watershed, since all of our waterways make their way to the Delaware River.