The term chronic refers to a process that often begins very gradually and then persists over a long period.
For example, ulcerative colitis--an inflammatory condition of unknown cause that is limited to the colon--is a chronic disease.
Its peak incidence is early in the second decade of life.
The disease is characterized by relapsing attacks of bloody diarrhea that persist for weeks to months.
These attacks alternate with asymptomatic periods that can last from weeks to years.

The terms benign and malignant, most often used to describe tumors, can be used in a more general sense. 

Benign diseases are generally without complications, and a good prognosis (outcome) is usual.
A wart on the skin is a benign tumor caused by a virus; it produces no illness and usually disappears spontaneously if given enough time (often many years). 

Malignancy implies a process that, if left alone, will result in fatal illness.
Cancer is the general term for all malignant
tumors.


Diseases usually are indicated by signs and symptoms. 

A sign is defined as an objective manifestation of disease that can be determined by a physician; 

A symptom is subjective evidence of disease reported by the patient. 

At the most elemental level, disease develops when any disruptive or adverse influence overcomes the homeostatic and defensive controls of the body.
As will be seen, there are numerous influences that can tip the scales of health toward disease.

The human body acts as a unit--an individual--both in health and in disease.

 Medical and Alternative Medical Terminology, Explanations -  by Courtesy of Encyclopedia Britannica® 2001