reckoner vs reckon

reckoner is a noun but reckon is not a noun.

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

reckoner (noun)	reckon (noun)
a handbook of tables used to facilitate computation
an expert at calculation (or at operating calculating machines)

reckoner (verb)	reckon (verb)
	deem to be
	make a mathematical calculation or computation
	expect, believe, or suppose
	judge to be probable
	have faith or confidence in
	take account of