noun

1. the act, fact, or manner of falling upon or influencing
2. the degree or range of occurrence or effect; extent of influence
3. Informal an individual or particular occurrence or happening; instance or occasion several incidences of the disease in our village
4. Geom. partial coincidence between two figures, as of a line and a point contained in it
5. Physics
   1. the falling of a line, or a ray of light, projectile, etc. moving in a line, on a surface
   2. the direction of such falling

Etymology: ME (North) < OFr < LL incidentia