oftenness vs frequence

oftenness and frequence both are nouns.

Word	Noun	Adjective	Verb	Adverb
oftenness	Yes	No	No	No
frequence	Yes	No	No	No

As nouns, oftenness and frequence are synonyms defined as:

oftenness and frequence: the number of occurrences within a given time period

Other synonyms of oftenness include frequency.

oftenness (noun)	frequence (noun)
the number of occurrences within a given time period	the number of occurrences within a given time period