residency vs occupancy

residency and occupancy both are nouns.

Word	Noun	Adjective	Verb	Adverb
residency	Yes	No	No	No
occupancy	Yes	No	No	No

As nouns, occupancy is a hyponym of residency; that is, occupancy is a word with a more specific, narrower meaning than residency:

Other hyponyms of residency include lodging, tenancy.

residency (noun)	occupancy (noun)
the act of dwelling in a place	an act of being a tenant or occupant
the position of physician who is receiving special training in a hospital (usually after completing an internship)	the act of occupying or taking possession of a building