reckoner vs actuary

reckoner and actuary both are nouns.

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

As nouns, actuary is a hyponym of reckoner; that is, actuary is a word with a more specific, narrower meaning than reckoner:

reckoner: an expert at calculation (or at operating calculating machines)
actuary: someone versed in the collection and interpretation of numerical data (especially someone who uses statistics to calculate insurance premiums)

Other hyponyms of reckoner include adder, number cruncher, statistician, subtracter.

reckoner (noun)	actuary (noun)
a handbook of tables used to facilitate computation	someone versed in the collection and interpretation of numerical data (especially someone who uses statistics to calculate insurance premiums)
an expert at calculation (or at operating calculating machines)