Incidence may refer to: Incidence (epidemiology), a measure of the risk of developing some new condition within a specified period of time Incidence (geometry), the binary relations describing how subsets meet Angle of incidence, a measure of deviation of something from "straight on" Incidence algebra, associative algebra used in combinatorics, a branch of mathematics Incidence structure, a feature of combinatorial mathematics Incidence, a market research term describing the percent of a p… (More on Incidence)