logician vs expert

logician and expert both are nouns.

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

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

logician (noun)	expert (noun)
a person skilled at logic	a person with special knowledge or ability who performs skillfully

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