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1. The number of specified new events, e.g., persons falling ill with a specified disease, during a specified period in a specified population. 2. In optics, intersection of a ray of light with a surface. [L. incido, to fall into or upon, to happen]
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1 a) ANGLE OF INCIDENCE
b) the arrival of something (as a ray of light) at a surface
2 a) an act or the fact or manner of occurring or affecting <diseases of domestic \incidence (Science)>
b) rate of occurrence or influence esp the rate of occurrence of new cases of a particular disease in a population being studied compare PREVALENCE
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in·ci·dence (inґsĭ-dəns) [L. incidere to occur, to happen] 1. the rate at which a certain event occurs, e.g., the number of new cases of a specific disease occurring during a certain period in a population at risk (see incidence rate, under rate). Cf. prevalence. 2. the arrival of radiant energy at a surface.Medical dictionary. 2011.