efficiency expert vs expert

efficiency expert and expert both are nouns.

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

As nouns, expert is a hypernym of efficiency expert; that is, expert is a word with a broader meaning than efficiency expert:

efficiency expert: an expert in increasing the efficient use of machines and personnel
expert: a person with special knowledge or ability who performs skillfully

efficiency expert (noun)	expert (noun)
an expert in increasing the efficient use of machines and personnel	a person with special knowledge or ability who performs skillfully

efficiency expert (adjective)	expert (adjective)
	having or showing knowledge and skill and aptitude
	of or relating to or requiring special knowledge to be understood