What is Incidence?

Incidence definition and meaning on Dictionary terms:
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. the striking of a ray of light, beam of electrons, etc., on a surface, or the direction of striking. 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.