To contravene means to go against or break a rule, law, or agreement. When a company's advertising contravenes truth-in-advertising laws, it means the ads violate those legal requirements. When a school policy contravenes students' rights, the policy conflicts with rules about what schools can and cannot do.

The word often appears in formal contexts, especially legal or official ones. You might read that a new regulation contravenes an existing law, meaning the two rules clash and can't both be followed. A treaty between countries might state that neither side can take actions that contravene the agreement's terms.

Contravene is similar to violate or break, but it's more formal and often implies a direct conflict between two rules or principles. When someone contravenes a policy, they're doing something that directly opposes what the rule says. For instance, if your town has a rule requiring permits for yard sales, holding one without a permit would contravene that ordinance.