subcontrary

/ˌsʌbˈkɑntrɛri/
adjective
  1. Relating to a pair of statements in logic that can both be true but cannot both be false.
    • The subcontrary relationship between 'some are happy' and 'some are not happy' allows both to be true.
    • In the debate, they examined the subcontrary nature of the two claims.
    • Understanding subcontrary propositions helps in analyzing arguments.
noun
  1. A statement that is the subcontrary of another; one of a pair of subcontrary propositions.
    • The logician identified each subcontrary in the argument.
    • If one subcontrary is false, the other must be true.
    • She wrote down the subcontrary to compare it with the original claim.