Part of speech: Noun
a handbook of tables used to facilitate computation
Categories: Handbook, Enchiridion, Vade mecum
The word "reckoner" comes from Middle English reknere. Many other languages have similar words:
reckon – A related word in the same word family.
-er – A related word in the same word family.
Middle English had more flexible word order than Modern English because it retained more inflections.