Epidemic, from the Greek meaning "prevalent among the people," is most commonly used to describes an outbreak of an illness or disease in which the number of individual cases significantly exceeds the usual or "expected" number of cases in any given population. In the United States, the Centers for Disease Control (CDC) takes the average cases of, let's say, influenza, in 122 cities nationwide over the preceding five years. If influenza cases in any area significantly exceed that percentage baseline, it is said to be of epidemic proportions. The term is also used to describe almost any occurrence which increases drastically or becomes rampant--for example, auto thefts from parking lots or a significant increase in gang-related violence. Pandemic, which means "all the people," describes and epidemic which occurs in more than one country or population simultaneously. An excellent example of a disease which has reached...