settling vs subsidence

settling and subsidence both are nouns.

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

As nouns, settling and subsidence are synonyms defined as:

Other synonyms of settling include subsiding.

settling (noun)	subsidence (noun)
a gradual sinking to a lower level	a gradual sinking to a lower level
	the sudden collapse of something into a hollow beneath it
	an abatement in intensity or degree (as in the manifestations of a disease)