reckoner vs subtracter

reckoner and subtracter both are nouns.

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

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

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

reckoner (noun)	subtracter (noun)
a handbook of tables used to facilitate computation	a machine that subtracts numbers
an expert at calculation (or at operating calculating machines)	a person who subtracts numbers