biconditional

[bahy-kuh n-dish-uh-nl]
adjective Logic.
  1. (of a proposition) asserting that the existence or occurrence of one thing or event depends on, and is dependent on, the existence or occurrence of another, as “A if and only if B.”

Origin of biconditional

First recorded in 1935–40; bi-1 + conditional
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British Dictionary definitions for biconditional

biconditional

noun
  1. another name for equivalence (def. 2)
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012