deficiency vs deficit

deficiency and deficit both are nouns.

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

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

deficiency: lack of an adequate quantity or number
deficit: the property of being an amount by which something is less than expected or required

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

Other hyponyms of deficiency include absence, dearth, famine, shortage, mineral deficiency, shortness, stringency, tightness.

deficiency (noun)	deficit (noun)
lack of an adequate quantity or number	the property of being an amount by which something is less than expected or required
the state of needing something that is absent or unavailable	an excess of liabilities over assets (usually over a certain period)
	(sports) the score by which a team or individual is losing
	a deficiency or failure in neurological or mental functioning