Disease (Old French disease = lack of ease) is a disorder in a human, Animal for plant caused by infection,
diet or by faulty functions of a process.
Types of disease. (i) on the basis of duration. Acute or chronic diseases.
(ii) on the basis of period of occurrence. Congenital and acquired diseases.
(iii) On the basis of causal agents. Infectious and non-infectious. Infectious or communicable diseases can be
contagious or non-contagious. Non-infectious disease may be deficiency disease, metabolic disease,
degenerative disease, allergy, cancer and injury.
Example of infectious disease. Influenza, tuberculosis, pneumonia.
Example of non-infectious disease. Cancer, diabetes.