Relating to, involving, or of the nature of a contradiction; inconsistent or mutually exclusive.
From 'contradiction' (from Latin 'contradictio') plus the adjective suffix '-al' (relating to, having the nature of).
Logic uses 'contradictional' relationships to prove things—if you can show that an idea and its opposite can't both be true at the same time, you've found a contradiction that helps you determine truth.
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