efficient vs efficiency

efficient is not a noun while efficiency is a noun.

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

efficient (noun)	efficiency (noun)
	skillfulness in avoiding wasted time and effort
	the ratio of the output to the input of any system

efficient (adjective)	efficiency (adjective)
being effective without wasting time or effort or expense
able to accomplish a purpose; functioning effectively