When a person is affected by a disease either the functioning or the appearance of one or more systems of the body will change for the worse.
Types of Diseases
(i) Acute Diseases : Acute diseases which last for only very short period of time and affect body suddenly and quickly. E.g., Cold, cough, typhoid etc.
(ii) Chronic Diseases : The diseases which last for a long time, even as much as a life time, are called chronic diseases. E.g., Diabetes, tuberculosis, elephantiasis etc.