ace vs expert

ace and expert both are nouns.

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

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

ace (noun)	expert (noun)
a serve that the receiver is unable to reach	a person with special knowledge or ability who performs skillfully
one of four playing cards in a deck having a single pip on its face
someone who is dazzlingly skilled in any field
the smallest whole number or a numeral representing this number

ace (adjective)	expert (adjective)
of the highest quality	having or showing knowledge and skill and aptitude
	of or relating to or requiring special knowledge to be understood