incidence

noun

1. the rate or range of occurrence or influence of something, especially of something unwanted: the high incidence of heart disease in men over 40.
2. a falling upon, affecting, or befalling; occurrence: The incidence of murder that Sunday afternoon shocked the sleepy village.
3. 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).
4. the fact or the manner of being incident.
5. Geometry. partial coincidence of two figures, as of a line and a plane containing it.

noun

1. degree, extent, or frequency of occurrence; amounta high incidence of death from pneumonia
2. the act or manner of impinging on or affecting by proximity or influence
3. physics the arrival of a beam of light or particles at a surfaceSee also angle of incidence
4. geometry the partial coincidence of two configurations, such as a point that lies on a circle

n.

1. The extent or rate of occurrence, especially the number of new cases of a disease in a population over a period of time.
2. The arrival of radiation or a projectile at a surface.