Толковый словарь английского языка Oxford English Reference - incidence

n. 1 (often foll. by of) the fact, manner, or rate, of occurrence or action. 2 the range, scope, or extent of influence of a thing. 3 Physics the falling of a line, or of a thing moving in a line, upon a surface. 4 the act or an instance of coming into contact with a thing. Phrases and idioms angle of incidence the angle which an incident line, ray, etc., makes with the perpendicular to the surface at the point of incidence. Etymology: ME f. OF incidence or med.L incidentia (as INCIDENT)