Making sense of the coronavirus pandemic requires getting up to speed on semantics as much as epidemiology.

Government officials and health care professionals toss off mentions of mortality rates, flattening the curve and lockdowns, assuming that we know what they mean. But the terms mean different things from country to country, state to state, even city to city and person to person.

Officials use the same phrases about mass testing, caseloads and deaths to describe very different situations. That makes it hard to give clear answers to vital questions: How bad are things? Where are they headed?

People search for insight by comparing their countries to those that are further along in the epidemic. But if the terms are misleading or used in differing ways, the comparisons are flawed. Also, the statistics and vocabulary offer a false sense of precision while in reality, the information we have shows only a fraction of what’s going on.