What does contrapositive mean?

It is the opposite of a statement...kinda... It is used in if then statements. Let me explain: Statement: If cardinals are red, then a dog is a cardinal. The contrapositive of that statement would be: If a dog is not a cardinal, then it is not red. Notice how you switch the order of if and then in the sentence. Then you insert the nots. To make the sentence true of false. I took geometry a while ago, sot his may not be accurate, but I hoped it helped!