Greek 'epi-' (upon) + 'demos' (people) + 'logos' (study) — literally 'the study of what falls upon the people.'
Definition
The branch of medicine which deals with the incidence, distribution, and possible control of diseases and other factors relating to health.
The Full Story
Greek19th centurywell-attested
From Greek 'epidḗmios' (ἐπιδήμιος, prevalent amongthe people, visiting), from 'epí' (ἐπί, upon, among) + 'dêmos' (δῆμος, people, district, the common people), combined with '-logía' (study of, from 'lógos,' word, reason). The compound is literally 'the study of what falls upon the people' — the science of tracking disease patterns across populations. Greek 'dêmos' derives from PIE *deh₂-mo- (division of people), from *deh₂- (to divide), which also produced Greek 'daíomai' (to divide) and
. The modern discipline of epidemiology was founded by John Snow during the 1854 London cholera outbreak, when he mapped cases to trace the disease to a contaminated water pump on Broad Street — a founding moment of data-driven public health. Key roots: epi- (Greek: "upon, among, over"), dēmos (Greek: "people, district, populace").