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

The results showed that morning larks had a lower incidence of breast cancer. Cathleen O'grady, Ars Technica, "Being a morning person might have some health advantages," 12 Nov. 2018 Some even refuse to work with those who have been diagnosed because of the high incidence of these tendencies. Molly Burford, Allure, "9 Things You Should Know About Borderline Personality Disorder, From Someone Who Has It," 8 Oct. 2018 And the incidence and potential for crises mounts annually. New York Times, "Preventing Suicide Among College Students," 2 July 2018 Because cardiac arrest can and does happen anywhere, both incidences, officials said, underscore the need for ordinary people to learn the principles of basic life support. Donna Vickroy, Daily Southtown, "Want to be a superhero? Know that CPR and AEDs save more lives than capes and masks," 29 June 2018 Twin studies compare disease incidence in identical and fraternal twins, using huge data sets of twin pairs. Ruth O. Selig, Washington Post, "Years ago when my twin got breast cancer I took drastic action and am grateful I did," 28 May 2018 Through the years, his immature behavior has resulted in uneven performances, as well as fines for not trying hard enough and off-color disputes and incidences. Sandra Harwitt, USA TODAY, "Nick Kyrgios on his emotions in a match: 'It's a tug of war all the time'," 3 July 2018 The death tolls are further exacerbated by torture, denial of adequate medical care and high incidence of work accidents, said a 2014 United Nations report on North Korea. Kim Tong-hyung, Fox News, "A look at N. Korea's human rights abuses Trump played down," 13 June 2018 Residents in the area blame the plant for high incidences of cancer. Parth M.n.,, "Indian court stops construction at copper plant after 11 killed in protests," 23 May 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

1 Dec 2018

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Time Traveler for incidence

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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