hypocrisy
Saying you believe something but acting in the opposite way.
Hypocrisy is when someone claims to believe something or hold certain standards but then acts in ways that completely contradict those beliefs. A hypocrite might lecture others about honesty while lying, or insist that everyone follow rules they secretly break.
Imagine a student who constantly complains about classmates copying homework, calling it unfair and wrong, but then copies someone else's assignment when they forget to do their own. That's hypocrisy: the gap between what someone says is right and what they actually do.
Hypocrisy appears in many situations. A sibling might demand that family rules apply strictly to you but make excuses when they break the same rules. A friend might criticize others for gossiping while spreading rumors themselves. What makes it hypocrisy is the combination of judging others harshly for behavior you excuse in yourself. Everyone makes mistakes or fails to live up to ideals sometimes, but hypocrisy specifically involves holding others to standards you don't apply to yourself.
People find hypocrisy especially frustrating because it feels dishonest and unfair. When someone discovers you've been hypocritical, they may lose trust in your words and judgment. Actions speak louder than words, and hypocrisy is when those two things shout completely different messages.