subcontrary

[ suhb-kon-trer-ee ]
/ sʌbˈkɒn trɛr i /

noun, plural sub·con·tra·ries. Logic.

one of two propositions that can both be true but cannot both be false.

Origin of subcontrary

1595–1605; < Medieval Latin subcontrārius, Late Latin (see sub-, contrary), orig. as translation of Greek hypenantíos
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for subcontrary

subcontrary
/ (sʌbˈkɒntrərɪ) logic /

adjective

(of a pair of propositions) related such that they cannot both be false at once, although they may be true togetherCompare contrary (def. 5), contradictory (def. 3)

noun plural -ries

a statement that cannot be false when a given statement is false
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