In a story about a workplace shooting involving three immigration officers, Reuters reporter Dan Whitcomb writes
Authorities described the shooting as an incidence of workplace violence…
and quotes a spokesman named Martinez:
The shooting, which Martinez described as an “isolated incident” that was still under investigation…
So which is it? Incidence or incident?
Both incident and incidence derive from the same medieval Latin word, but in modern usage the words have different meanings.
incident: noun. an occurrence or an event.
incidence: noun. the range or scope of a thing, the extent of its influence or effects.
Incident is the more common word. It can refer to any sort of happening, trivial or serious. A shooting is an incident. Meeting someone you haven’t seen in years while you’re at the Mall is an incident. The classic western with Henry Fonda and Dana Andrews is The Ox-bow Incident.
Incidence is a more specialized word. In the study of human activity, researchers may speak of” the incidence of crime on college campuses,” or “the incidence of lung disease among miners.”
In geometry, incidence is “the situation of one locus with respect to another when they have a common point or points, but do not completely coincide.” In the vocabulary of flying, pilots increase or decrease lift by altering “the angle of incidence.”
This shooting incident may find its way into a study of the incidence of violence among government workers.
Bottomline: If all you mean is “event, happening,” or “occurrence,” say incident.
