1643, in the meaning defined above
Latin ratiocinatus, past participle of ratiocinari to reckon, from ratio + -cinari (as in vaticinari to prophesy) — more at vaticinate
Time Traveler for ratiocinate
See more words from the same year
From the Editors at Merriam-Webster
Galaxy Brain: 10 Words for Deep Thoughts
What's (another word for) the big idea?
Do You Need a New Language Peeve?
Sure, it's popular to complain about words ending in '-ize'. But what about words ending in '-ate'?
10 Sherlock Holmes Words Worth...
The language in Sherlock Holmes is as intriguing as the stories.
Cite this Entry
“Ratiocinate.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/ratiocinate. Accessed 3 Oct. 2022.
See Definitions and Examples »
Get Word of the Day daily email!
The Great British Vocabulary Quiz
Test your knowledge - and maybe learn something along the way.
A daily challenge for crossword fanatics.
Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!
As illustrated by some very smart pups
Bikini, bourbon, and badminton were places first
Do you take pride in Pride?
Look up any year to find out
How to use a word that (literally) drives some pe...
We're intent on clearing it up
Editor Emily Brewster clarifies the difference.
"The public is a hot mess"
Test your visual vocabulary!
Take the quiz
Level up your vocabulary with these newly added w...
Test your knowledge - and maybe learn something a...
Can you outdo past winners of the National Spelli...