incidence

noun

in·​ci·​dence ˈin(t)-sə-dən(t)s 

-ˌden(t)s

1

a

: rate of occurrence or influence

a high incidence of crime

b

: an act or the fact or manner of falling upon or affecting : occurrence

2

a

: angle of incidence

b

: the arrival of something (such as a projectile or a ray of light) at a surface

Did you know?

The words incident, incidence, and instance may seem similar (and, in fact, incident and incidence are closely related), but they are applied in different ways. In current use, incidence usually means "rate of occurrence" and is often qualified in some way ("a high incidence of bear sightings"). Incident usually refers to a particular event, often something unusual or unpleasant ("many such incidents go unreported"). Instance suggests a particular occurrence that is offered as an example ("another instance of a simple change bringing real improvement"); it can also be synonymous with case ("many instances/cases in which the wrong form was submitted"). The plural incidences sometimes occurs in such contexts as "several recent incidences of bear sightings," but this use is often criticized as incorrect.

Examples of incidence in a Sentence

an increased incidence of diabetes

a high incidence of criminal behavior

Recent Examples on the Web

Cancer incidence is also higher in certain racial minority populations—for example, the cancer mortality rate in Black men is 16 percent higher than in white men, and Hispanic people are almost twice as likely to acquire stomach or liver cancer than white people. —Barbara A. Perry, Newsweek, 28 Jan. 2025

Porsche was building exquisite lightweight sports cars long before the 917K came along, but the incidence of drivers who drove one in period who then went and bought one later in life is an interesting correlation. —New Atlas, 27 Jan. 2025

Another disturbing trend started in 2021 when, for the first time, lung cancer incidence in women under 65 surpassed the incidence in men: 15.7 cases per 100,000 women under 65, compared with 15.4 per 100,000 in men. —Roni Caryn Rabin, New York Times, 16 Jan. 2025

In 2007, cancer incidence in middle-aged women was 21 percent lower than in their male counterparts. —Sarah Fortinsky, The Hill, 16 Jan. 2025

Word History

First Known Use

1626, in the meaning defined at sense 2a

Phrases Containing incidence

• angle of incidence

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Kids Definition

incidence

noun

in·​ci·​dence ˈin(t)-səd-ən(t)s 

-sə-ˌden(t)s

1

: angle of incidence

2

: rate of occurrence

a high incidence of illness

Medical Definition

incidence

noun

in·​ci·​dence ˈin(t)-səd-ən(t)s, -sə-ˌden(t)s 

1

a

: angle of incidence

b

: the arrival of something (as a ray of light) at a surface

2

a

: an act or the fact or manner of occurring or affecting

diseases of domestic incidence

—Science

b

: rate of occurrence or influence

especially : the rate of occurrence of new cases of a particular disease in a population being studied compare prevalence