incidence

American  

[in-si-duhns] / ˈɪn sɪ dəns /

noun

1. the rate or range of occurrence or influence of something, especially of something unwanted.

   the high incidence of heart disease in men over 40.

2. a falling upon, affecting, or befalling; occurrence.

   The incidence of murder that Sunday afternoon shocked the sleepy village.

3. Optics, Physics.

   1. the striking of a ray of light, beam of electrons, etc., on a surface, or the direction of striking.

   2. angle of incidence.

4. the fact or the manner of being incident.

5. Geometry. partial coincidence of two figures, as of a line and a plane containing it.

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incidence British  

/ ˈɪnsɪdəns /

noun

1. degree, extent, or frequency of occurrence; amount

   a high incidence of death from pneumonia

2. the act or manner of impinging on or affecting by proximity or influence

3. physics the arrival of a beam of light or particles at a surface See also angle of incidence

4. geometry the partial coincidence of two configurations, such as a point that lies on a circle

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Etymology

Origin of incidence

First recorded in 1375–1425; late Middle English, from Late Latin incidentia. See incident, -ence

Explanation

Incidence means the frequency with which something bad occurs. You’ll hear of “incidences of cancer” or “incidences of war." You hope the incidence is decreasing, not increasing. You might confuse incidence and incident. They sound similar, but incident refers only to something that happened, not to the frequency with which it happens. After a car accident, the police file an incident report, which is a fancy way of saying they write down what happened. Looking at these reports grouped together can show you if the incidence of accidents at specific intersections in town is on the rise.

Example Sentences

"Public investments that expand access to enriching environments, like libraries and early education programs designed to spark a lifelong love of learning, may help reduce the incidence of dementia."

From Science Daily • Apr. 15, 2026

Caregiving incidence goes up to 31% among those with a parent who is 75 or older.

From MarketWatch • Feb. 26, 2026

The UK has the highest incidence of mesothelioma in the world, with around 2,700 people diagnosed each year – about 50 of those are in Northern Ireland.

From BBC • Feb. 19, 2026

What we’re going to have is a real-world experience of when unvaccinated people get measles, what is the new incidence of hospitalization?

From Los Angeles Times • Feb. 18, 2026

By 1950 the incidence of Dutch elm disease in New York City had been reduced to %o of 1 per cent of the city’s 55,000 elms.

From "Silent Spring" by Rachel Carson

Related Words

• extent
• frequency
• percentage
• prevalence
• proportion
• rate