/in"si deuhns/ , n.
1. the rate or range of occurrence or influence of something, esp. 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.
a. the striking of a ray of light, beam of electrons, etc., on a surface, or the direction of striking.
b. See angle of incidence (def. 1).
4. the fact or the manner of being incident.
5. Geom. partial coincidence of two figures, as of a line and a plane containing it.
[ 1375-1425; late ME incidentia. See INCIDENT, -ENCE ]