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

The lab is now investigating whether the same lysosomal dysfunction in old stem cells plays a role in leukemia, a disease whose incidence climbs sharply with age. —Allison Palmer, Fort Worth Star-Telegram, 15 June 2026

Over the past decade, these incidence analyses have described similar situations. —Keith M. Phaneuf, Hartford Courant, 15 June 2026

Given about 2 in 5 American adults are obese, curbing this chronic medical condition could have dramatic effects in decreasing the incidence of cancer. —Omer Awan, Forbes.com, 13 June 2026

This is especially concerning given that Black women experience the highest incidence of injury and death from intimate partner violence in the country. —Sativa Banks, The Conversation, 4 June 2026

Word History

First Known Use

1626, in the meaning defined at sense 2a

Phrases Containing incidence

• angle of incidence

Rhymes for incidence

• coincidence

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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