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

Liz Darlison, chief executive at Mesothelioma UK, said the country "shamefully has the highest incidence of mesothelioma in the world" with research urgently needed.

From BBC • Mar. 11, 2026

This could help explain some of the increasing incidence of chronic diseases among people in industrialized countries, he said.

From The Wall Street Journal • Mar. 3, 2026

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

From MarketWatch • Feb. 26, 2026

The researchers noted that these results align with findings from a similar study they previously conducted in Massachusetts, which found higher cancer incidence among people living closer to nuclear facilities.

From Science Daily • Feb. 24, 2026

Within the period covered by the rise of modern pesticides, the incidence of leukemia has been steadily rising.

From "Silent Spring" by Rachel Carson

Related Words

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