The occurrence, rate, or frequency of a disease, crime, or other undesirable thing. The incidence of flu cases has increased significantly this winter.
The way in which the burden of a tax falls upon different groups in the population. The incidence of the new tax policy is expected to affect low-income families the most.
The arrival of a beam, wave, or other force at a surface, especially as measured by the angle it makes with the surface. The angle of incidence affects the amount of light that is reflected.