efficiency vs economy

efficiency and economy both are nouns.

Word	Noun	Adjective	Verb	Adverb
efficiency	Yes	No	No	No
economy	Yes	No	No	No

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

efficiency (noun)	economy (noun)
skillfulness in avoiding wasted time and effort	an act of economizing; reduction in cost
the ratio of the output to the input of any system	frugality in the expenditure of money or resources
	the efficient use of resources
	the system of production and distribution and consumption