Epidemiology
Etymology
Built from Greek epi, "upon," demos, "the people," and -logia, "study" — the study of what falls upon a population. It shares its "upon the people" core with "epidemic." Rather than treating individuals, epidemiology tracks rates, causes, and risk factors across whole groups, which is why it drives public-health decisions and much of the health advice we hear.
noun · /ep-ih-dee-mee-OL-uh-jee/
The study of how diseases spread and how often they occur across populations.
What it names
The discipline behind headlines about risk and outbreaks — the science of patterns in groups rather than symptoms in one body.
Example
Epidemiology showed the outbreak clustered around one contaminated water source.
Related idea
Pathology studies disease inside the body; epidemiology studies its movement through populations.