Occasionally you might hear the expression about the exception proving the rule. Almost always it’s used incorrectly. People say “the exception proves the rule” meaning something like “the exception shows Proves) that the rule exists.” This is nonsense. This comic, last panel, is typical:
The word “proves” in this expression means “tests.” (It’s an old usage. You’ll find it in the KJV.) The real point of the expression is to assert that if you can break (test/prove) a rule and get away with it, it’s not a rule. If breaking the rule causes a violation, the rule is real.