deficiency vs inadequacy

deficiency and inadequacy both are nouns.

Word	Noun	Adjective	Verb	Adverb
deficiency	Yes	No	No	No
inadequacy	Yes	No	No	No

As nouns, deficiency and inadequacy are synonyms defined as:

Other synonyms of deficiency include insufficiency.

deficiency (noun)	inadequacy (noun)
lack of an adequate quantity or number	unsatisfactoriness by virtue of being inadequate
the state of needing something that is absent or unavailable	lack of an adequate quantity or number
	a lack of competence