Said something opposite to what someone else said, or acted in a way that goes against your own words.
From Latin contradictus (spoken against), from contra- (against) and dicere (to speak). The term entered Middle English through Old French and has meant logical opposition for 700+ years.
The mathematical concept of contradiction (something can't be both true and false at once) comes from this word's root meaning 'speaking against'—so logic itself is named after the image of two people saying opposite things.
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