subsidence vs hiatus

subsidence and hiatus both are nouns.

Word	Noun	Adjective	Verb	Adverb
subsidence	Yes	No	No	No
hiatus	Yes	No	No	No

As nouns, hiatus is a hypernym of subsidence; that is, hiatus is a word with a broader meaning than subsidence:

subsidence: an abatement in intensity or degree (as in the manifestations of a disease)
hiatus: an interruption in the intensity or amount of something

Other hypernyms of subsidence include abatement, reprieve, respite, suspension.

subsidence (noun)	hiatus (noun)
a gradual sinking to a lower level	a natural opening or perforation through a bone or a membranous structure
the sudden collapse of something into a hollow beneath it	a missing piece (as a gap in a manuscript)
an abatement in intensity or degree (as in the manifestations of a disease)	an interruption in the intensity or amount of something