incidence vs frequency

incidence and frequency both are nouns.

Word	Noun	Adjective	Verb	Adverb
incidence	Yes	No	No	No
frequency	Yes	No	No	No

As nouns, frequency is a hypernym of incidence; that is, frequency is a word with a broader meaning than incidence:

incidence: the relative frequency of occurrence of something
frequency: the ratio of the number of observations in a statistical category to the total number of observations

Other hypernyms of incidence include relative frequency.

incidence (noun)	frequency (noun)
the striking of a light beam on a surface	the number of observations in a given statistical category
the relative frequency of occurrence of something	the ratio of the number of observations in a statistical category to the total number of observations
	the number of occurrences within a given time period