Any deviation from the normal functioning or state of incomplete physical or mental well-being is called disease. Disease is a condition that impairs the proper functioning of the body or one of its parts. The diseases may be of different types, such as :
(a) Acute disease: A few diseases occur suddenly and last for a few days. Example: Common cold. jaundice
(b) Chronic disease: The diseases that occur over a period of time and last longer, or even for the lifetime are called chronic diseases. Example: Tuberculosis, diabetes.
(c) Infectious disease: Diseases that spread from one person to another. Example: Influenza, tuberculosis
(d) Non-infectious disease: They do not spread to others and they restrain within a person who has contracted them. Example: Cancer, marasmus.