Ratiocinate

The verb 'to ratiocinate' means 'to reason', 'to form a judgement by the use of logic or other controlled thinking'. The verb and its derivatives, such as the participles ratiocinated and ratiocinating, the noun ratiocination and the adjective ratiocinative are not in common use, even in academic English, but may sometimes be the only way to express an idea of the use of a mind.

• Pronunciation gives trouble. OED (2020) has this note: "British dictionaries down to the end of the 19th cent[ury] give the pronunciation of ratiocinate and its derivatives as having /ʃ/ in the second syllable and short o in the third syllable. All editions of D. Jones Eng[lish] Pronouncing Dictionary up to and including the 14th give only /t/ (with long o as an alternative in ratiocination only); the 15th edition gives the alternatives of /ʃ/ in the second and /əʊ/ in the third syllable. U.S. dictionaries mainly give /ʃ/ in the second syllable and short o in the third down to the mid 20th cent[ury]", which indicates some uncertainty.
• LPD (2000) has the following pronunciations:
  • for ratiocinate: 'rat-ee-OSS-in-ate' (IPA: /ˌræt i ˈɒs ɪ neɪt/), with the derivatives
  • 3rd person present tense 'rat-ee-OSS-in-ates' (IPA: /ˌræt i ˈɒs ɪ neɪts/)
  • -ed participle 'rat-ee-OSS-in-ated' (IPA: /ˌræt i ˈɒs ɪ neɪt ɪ (or ə)d /)
  • and -ing participle 'rat-ee-OSS-in-ate-ing' (IPA: /ˌræt i ˈɒs ɪ neɪt ɪŋ/).
  • The noun ratiocination is given as 'rat-ee-OSS-in-ashun' (IPA: /ˌræt i ˈɒs ɪ neɪʃ ^ən/).
• In all of these, 'rash-' (/ræʃ/) is listed as an alternative for the first syllable, and '-OH-' (/əʊ/) for the third vowel. LPD gives American variants as 'rash-' (/æʃ/) in the first syllable, and '-AH-' (/ɑː/) as the third vowel. OED adds 'raid-i-OHS-nate' (/ˌreɪd i ˈoʊs ˌneɪt/) or 'rash-ee-OHS-nate' (/ˌræʃ i ˈoʊs ˌneɪt/).

LPD doesn't list the adjective ratiocinative. OED gives pronunciations as

• • British /ˌratɪˈɒsᵻnətɪv/ ('rat-i-OSS-i-native') or /ˌraʃɪˈɒsᵻnətɪv/ ('rash-i-OSS-i-native')
  • and U.S. /ˌræʃiˈoʊsəˌneɪdɪv/ ('rash-i-OHS-e^r-nade-ive').

See also Rational - rationale.