[in-si-duh ns]


the rate or range of occurrence or influence of something, especially of something unwanted: the high incidence of heart disease in men over 40.
a falling upon, affecting, or befalling; occurrence: The incidence of murder that Sunday afternoon shocked the sleepy village.
Optics, Physics.
  1. the striking of a ray of light, beam of electrons, etc., on a surface, or the direction of striking.
  2. angle of incidence(def 1).
the fact or the manner of being incident.
Geometry. partial coincidence of two figures, as of a line and a plane containing it.

Origin of incidence

First recorded in 1375–1425; late Middle English word from Late Latin word incidentia. See incident, -ence
Can be confusedincidence incidents incidental Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

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British Dictionary definitions for incidence



degree, extent, or frequency of occurrence; amounta high incidence of death from pneumonia
the act or manner of impinging on or affecting by proximity or influence
physics the arrival of a beam of light or particles at a surfaceSee also angle of incidence
geometry the partial coincidence of two configurations, such as a point that lies on a circle
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for incidence

early 15c., "incidental matter," from Middle French incidence (15c.), from Late Latin incidentia (see incident (n.)). Meaning "act of coming into contact with" is from 1650s; sense in physics is from 1620s.

Online Etymology Dictionary, © 2010 Douglas Harper

incidence in Medicine




The extent or rate of occurrence, especially the number of new cases of a disease in a population over a period of time.
The arrival of radiation or a projectile at a surface.
Related formsinci•dent adj.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.