reckoner vs expert

reckoner and expert both are nouns.

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

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

reckoner (noun)	expert (noun)
a handbook of tables used to facilitate computation	a person with special knowledge or ability who performs skillfully
an expert at calculation (or at operating calculating machines)

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