Final answer:
An 'epidemic' is a disease occurrence that affects a large number of individuals within a population at the same time, much higher than expected. 'Demos' translates to 'the people' and is part of 'epidemiology', the study of disease patterns in populations. Epidemics are contrasted with pandemics, which are global disease outbreaks, and endemic diseases, which are constantly present at a low incidence.
Step-by-step explanation:
In biology, the term epidemic refers to a disease that occurs in an unusually high number of individuals in a population at the same time. The science that studies these patterns of disease occurrence is called epidemiology. An epidemic is different from a pandemic, which is a widespread, often worldwide, epidemic. Diseases that are always present in a population, usually at a low rate, are described as endemic. Demos, a Greek word, loosely translates to 'the people' and is part of the word epidemiology, indicating that this science is concerned with health events as they affect groups of people, or populations.
Epidemics may vary in scope and impact, ranging from local community outbreaks to events of national or even global significance. Examples of epidemic diseases are flu (influenza) and epidemic typhus. The occurrence of an epidemic implies a higher-than-expected incidence of a disease within a given time period for a specified population.