Incidence

How to spell incidence

9 letters · 3 syllables

How to pronounce incidence

Say the part in capitals loudest.

What does incidence mean?

1. nounThe frequency or extent to which something happens, especially measured across a population.
2. nounThe way in which a ray of light, sound, or radiation strikes a surface, measured as an angle from the perpendicular.

Incidence in a sentence

• The study tracked the incidence of diabetes across three regions.

• The angle of incidence equals the angle of reflection.

• A higher incidence of theft was reported in the warehouse district.

• Changing the angle of incidence altered how the laser bounced off the mirror.

Where does incidence come from?

Language of origin: Latin

This word descends from the Latin verb incidere, meaning 'to fall upon' or 'to happen to', which was built from in- ('on, upon') and cadere ('to fall'). The same cadere root gives us 'cadence', 'accident', and 'coincidence', all carrying the buried image of something falling into place or befalling a person. Late Latin formed the noun incidentia for 'a falling upon', and English took the word in through French during the 1400s, at first meaning simply an occurrence or something that happens. Over time it narrowed to its modern uses: the rate at which something happens (especially in statistics and medicine) and, in physics, the manner in which a ray of light or radiation falls onto a surface. The spelling trap is the ending: 'incidence' is an abstract noun ending in -ence, not the plural 'incidents', which sounds almost identical but means several separate events.

How the word is built

• in- (on, upon)
• cid (from Latin cadere: to fall)
• -ence (noun suffix forming a state or quality)