ratiocinate

From Latin ratiocinor (“to reckon, argue”).

• (General American) IPA^(key): /ˌɹætiˈosəˌneɪt/, /ˌɹæʃiˈɑsəˌneɪt/

ratiocinate (third-person singular simple present ratiocinates, present participle ratiocinating, simple past and past participle ratiocinated)

1. To use the powers of the mind logically and methodically; to reason.
   • 1887, Robert Louis Stevenson, The Treasure of Franchard, ch. 6:

     "Observe the relative position," returned the Doctor with a smile. "It is your attitude to believe through thick and thin in one man's judgment—your own. I follow the same opinion, but critically and with open eyes. Which is the more irrational—I leave it to yourself."

     "Oh, my dear fellow!" cried Casimir, " […] don't ratiocinate with me."

• ratiocination

ratiōcināte

1. vocative masculine singular of ratiōcinātus