<P> A disease is any condition which results in the disorder of a structure or function in a living organism that is not due to any external injury . The study of disease is called pathology , which includes the study of cause . Disease is often construed as a medical condition associated with specific symptoms and signs . It may be caused by external factors such as pathogens or by internal dysfunctions , particularly of the immune system , such as an immunodeficiency , or by a hypersensitivity , including allergies and autoimmunity . </P>
which term means the study of the nature and causes of disease
pathology