in·ci·dence | \ˈin(t)-sə-dən(t)s, -ˌden(t)s\

Definition of incidence 

1a : angle of incidence

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

2a : an act or the fact or manner of falling upon or affecting : occurrence

b : rate of occurrence or influence a high incidence of crime

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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

Still, there are incidences when unruly audiences shut down speeches, particularly outside the U.S. Mari Uyehara, GQ, "How Free Speech Warriors Mainstreamed White Supremacists," 8 May 2018 One of the most common incidental findings that the CAT scans showed was a 10 percent incidence of tuberculosis. David Becker,, "Lessons on heart disease from the jungles of Bolivia," 8 Jan. 2018 So markers that have been associated with cancer incidence should be left out—that would be one solution. Matt Warren, Science | AAAS, "Crime scene DNA could be used to reveal a suspect’s age—and whether they have cancer," 3 July 2018 Willett says that could slash the rates of preliminary death from heart disease, and reduce the incidence of diabetes, dementia and other metabolic diseases. Author: Caitlin Dewey, Anchorage Daily News, "Artificial trans fats, widely linked to heart disease, are officially banned," 19 June 2018 That’s not a complicated algorithm for reducing the incidence of hearing loss in patients and instructors. Julia Belluz, Vox, "How your cycling class could give you hearing loss," 31 May 2018 That was the highest incidence of any group of men, according to the study. Karen Kaplan,, "The death rate from cancer is falling for American men, women and children of all backgrounds," 22 May 2018 Here is that passage in full: This is the reason that, for example, Orientals have less incidence of crime than whites. Anne Branigin, The Root, "Trump, the Walking Internet Comments Section, Taps Racist Blogger for Federal Job," 3 Mar. 2018 On that note, the incidence of diarrhea was just 17 percent, far below estimates for the Appalachian Trail (68 percent in 1988; 56 percent in 1997). Alex Hutchinson, Outside Online, "Here's What It Takes to Hike the John Muir Trail," 11 July 2018

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 1a

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Last Updated

6 Oct 2018

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The first known use of incidence was in 1626

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English Language Learners Definition of incidence

: the number of times something happens or develops : the rate at which something occurs

: 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 \

Medical Definition of incidence 

1a : angle 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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More from Merriam-Webster on incidence

Spanish Central: Translation of incidence

Nglish: Translation of incidence for Spanish Speakers

Britannica English: Translation of incidence for Arabic Speakers

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