in·​ci·​dence | \ ˈin(t)-sə-dən(t)s How to pronounce incidence (audio) , -ˌden(t)s \

Definition of incidence

1a : rate of occurrence or influence a high incidence of crime
b : an act or the fact or manner of falling upon or affecting : occurrence
b : the arrival of something (such as a projectile or a ray of light) at a surface

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Did You Know?

The words incident, incidence, and instance may seem similar (and, in fact, incident and incidence are closely related), but they are not used identically. In current use, incidence usually means "rate of occurrence" and is often qualified in some way ("a high incidence of diabetes"). 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 bureaucratic bumbling"); it can also be synonymous with case ("many instances in which the wrong form was submitted"). The plural incidences sometimes occurs in such contexts as "several recent incidences of crime," 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 Data showed the incidence of coronavirus cases in pupils quarantined due to exposure was about the same as those farther away in the classroom or outside the classroom but in the same grade. Bob Sandrick, cleveland, "Brecksville-Broadview Heights schools will return grades 5-12 pupils to classrooms 2 weeks earlier than planned," 18 Jan. 2021 The precautions keeping the coronavirus at bay are also sharply reducing the incidence of other diseases in the ranks, including influenza. Dave Philipps,, "New virus, old enemy," 17 Nov. 2020 The precautions keeping the coronavirus at bay are also sharply reducing the incidence of other diseases in the ranks, including influenza. Dave Philipps, New York Times, "New Virus, Old Enemy," 16 Nov. 2020 Despite that, Reg continues to post, say, that COVID-19 has a 99 percent survival rate and that there’s a high incidence of fraud in mail-in voting, neither of which is true. Steve Friess, The Atlantic, "The Trump Superfan Who Helped Two Gay Men Adopt a Baby," 1 Nov. 2020 Among the damage: a worsening incidence of cardiovascular disease and cancer and an alarming decline in immunization. Tunku Varadarajan, WSJ, "Epidemiologists Stray From the Covid Herd," 23 Oct. 2020 To enforce the protocol, test-and-trace call handlers will regularly contact those in self-isolation and police can check for compliance in high-incidence areas or among high-risk groups, the prime minister’s office said. Megan Durisin,, "U.K. to Fine as Much as $13,000 for Breaking Isolation Rules," 20 Sep. 2020 In the African American community, Ezike said the incidence of severe cases and deaths are higher than with other groups. Steve Sadin,, "Those attending large Thanksgiving celebration could reconvene for Christmastime funeral, state health director warns," 27 Oct. 2020 Americans were about 7% more likely to get the vaccine if incidence of major adverse effects was 1 in 1 million as opposed to 1 in 10,000, and about 5% were more likely to get the vaccine if its duration of protection was five years instead of one. Adrianna Rodriguez, USA TODAY, "What will sway Americans to take a COVID-19 vaccine? Efficacy, adverse effects and politics, survey says," 20 Oct. 2020

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'incidence.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of incidence

1626, in the meaning defined at sense 2a

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The first known use of incidence was in 1626

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Last Updated

25 Jan 2021

Cite this Entry

“Incidence.” Dictionary, Merriam-Webster, Accessed 27 Jan. 2021.

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More Definitions for incidence


How to pronounce incidence (audio)

English Language Learners Definition of incidence

: the number of times something happens or develops : the rate at which something occurs
technical : the angle at which a ray (such as a ray of light) hits a surface


in·​ci·​dence | \ ˈin(t)-səd-ən(t)s, -sə-ˌden(t)s How to pronounce incidence (audio) \

Medical Definition of incidence

b : the arrival of something (as a ray of light) at a surface
2a : an act or the fact or manner of occurring or affecting diseases of domestic incidenceScience
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

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