1. to say or assert the opposite of what someone else has said
2. to be inconsistent with or go against something

Examples

• She contradicts everything her brother says.
• The witness contradicts the defendant's story.
• His actions contradict his words about caring for the environment.
• The new evidence contradicts the original theory.
• Don't contradict your teacher in front of the class.
• The data contradicts our initial hypothesis.
• He always contradicts himself when he's nervous.