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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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 Leukine is more widely and consistently used to reduce the incidence of severe and life-threatening infections in cancer patients undergoing chemotherapy as part of their treatment. Parija Kavilanz, CNN, 29 Mar. 2022 If these researchers succeed, such vaccines might dramatically reduce the incidence of mononucleosis and some cancers. Lydia Denworth, Scientific American, 13 Jan. 2022 More than ever, the decision appears to be influenced by local conditions, with many cities and regions of the country experiencing considerable variation in the incidence of Covid-19 cases. Michael T. Nietzel, Forbes, 16 Apr. 2022 Radiation damages living cells, and research has linked a decrease in ozone levels to an uptick in the incidence of skin cancer and cataracts in humans. Nidhi Subbaraman, WSJ, 17 Mar. 2022 However, the current high incidence of marijuana usage means that such rules will screen out many competent job applicants. Bill Conerly, Forbes, 12 Apr. 2022 Is the future incidence of T2d a threat to bankrupt our health care system? Bryant Stamford, The Courier-Journal, 7 Apr. 2022 And over the years complications from radiation exposure caused the incidence of cancer, particularly leukemia, to soar. Katie Hafner, Scientific American, 7 Apr. 2022 Among the findings: Young males ages 12-17 saw the highest incidence of cardiac events, during a post-vaccine window, among vaccinated individuals. Erin Prater, Fortune, 2 Apr. 2022 See More

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

13 May 2022

Cite this Entry

“Incidence.” Dictionary, Merriam-Webster, Accessed 28 May. 2022.

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More Definitions for incidence


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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