obvert
/ɒbˈvɜːt/verb
with obj.
- Logic alter (a proposition) so as to infer another proposition with a contradictory predicate, e.g. 'no men are immortal' to 'all men are mortal'【逻】反换（命题）。
派生词
obversion
noun词源
early 17th cent. (in the sense turn something until it is facing)： from Latin obvertere, from ob- 'towards' + vertere 'to turn'.