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

There has been a notable increase in incidence rates for many cancer types among women and younger adults, research shows. —Mary Kekatos, ABC News, 4 Apr. 2025

The incidence of dementia was then compared between people on either side of September 2, 1933. —John Timmer, ArsTechnica, 3 Apr. 2025

Correlation isn’t causation, but the incidence of seasonal allergies stands at 25% for adults, compared with 10% of all Americans in 1970, according to the U.S. Global Change Research Program. —Mark Gongloff, Mercury News, 1 Apr. 2025

According to a 2023 study, the incidence of mild pediatric TBI (pTBI) increased in Finland between 1998 and 2018. —New Atlas, 29 Mar. 2025

Word History

First Known Use

1626, in the meaning defined at sense 2a

Phrases Containing incidence

• angle of incidence

Rhymes for incidence

• coincidence

Podcast

Get Word of the Day delivered to your inbox!

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