epidemic
/ˌepɪˈdemɪk/·에피데믹·noun, adjective
a widespread occurrence of a disease
GreekCEFR B2
Root
epi- (upon, among) + Greek 'dēmos' (people)
Greek epidēmia (a stay among the people, prevalence) → French épidémie → English epidemic
In a word
epi- (upon) + dem (people) = 'what settles over the people'. The Greeks called anything that overflowed an individual into a community epidēmia. By root, an epidemic is "something staying among the people" — not just disease. Swap epi- for pan- (all) and you get pandemic — covering all the people.
Examples
The flu epidemic spread quickly.
Obesity is becoming an epidemic in many countries.
Local hospitals prepare for the next epidemic.
Related
democracydemographicpandemicendemicepidemiology