- 2 Physics the intersection of a line, or something moving in a straight line, such as a beam of light, with a surface. See also angle of incidence.
Incidence and incidents sound the same, but incidence is more often used in technical contexts, referring to the frequency with which something occurs: increased ultraviolet light is likely to cause increased incidence of skin cancer. Incidents is simply the plural of incident, an event: the police are supposed to investigate any incidents of domestic violence. The form incidences should be avoided.