different between obversion vs obvert

English

Latin obversio (“a turning towards”).

obversion (countable and uncountable, plural obversions)

The act of turning toward or downward.
(logic) An immediate inference that denies the opposite of something previously affirmed.
All men are mortal, so, by obversion, no men are immortal.
- 1870, Alexander Bain, Logic: Induction
  From 'warmth is agreeable' we can affirm, by formal obversion, 'warmth is not disagreeable, and not indifferent.' We cannot affirm, without an examination of the subject matter, 'cold is disagreeable.'

obvert (third-person singular simple present obverts, present participle obverting, simple past and past participle obverted)

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