Other forms: contradictories
A contradictory statement is one that says two things that cannot both be true. An example: My sister is jealous of me because I'm an only child.
Contradictory is related to the verb contradict, which means to say or do the opposite, and contrary, which means to take an opposite view. When witnesses give contradictory accounts of crimes—one saying the assailant had a knife and the other a gun—police officers often assume that at least one of the witnesses is lying.