incumbency vs incumbent

incumbency and incumbent both are nouns.

Word	Noun	Adjective	Verb	Adverb
incumbency	Yes	No	No	No
incumbent	Yes	Yes	No	No

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

incumbency (adjective)	incumbent (adjective)
	currently holding an office
	necessary (for someone) as a duty or responsibility; morally binding
	lying or leaning on something else