incidence
in.ci.dence \'in(t)-s*d-*n(t)s, -s*-.den(t)s\ n 1a: an act or the fact or manner of falling upon or affecting : OCCURR ENCE 1b: rate of occurrence or influence 2a: the arrival of something (as a projectile or a ray of light) at a surfa ce 2b: ANGLE OF INCIDENCE