term of office vs incumbency

term of office and incumbency both are nouns.

Word	Noun	Adjective	Verb	Adverb
term of office	Yes	No	No	No
incumbency	Yes	No	No	No

As nouns, term of office and incumbency are synonyms defined as:

term of office and incumbency: the term during which some position is held

Other synonyms of term of office include tenure.

term of office (noun)	incumbency (noun)
the term during which some position is held	the office of an incumbent
	a duty that is incumbent upon you
	the term during which some position is held