inadequacy vs deficiency

inadequacy and deficiency both are nouns.

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

As nouns, inadequacy and deficiency are synonyms defined as:

Other synonyms of inadequacy include insufficiency.

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