The logically equivalent restatement of a conditional in which both terms are negated and their order is reversed: P → Q restated as ¬Q → ¬P. A conditional and its contrapositive always have the same truth value — they are two surface forms of one underlying rule. On the LSAT, writing the contrapositive of every conditional is non-negotiable, because the test routinely presents inferences from the contrapositive direction ("no one who is not great at solving mysteries can be police chief" = "police chief → great at mysteries"). The contrapositive is the engine of Modus Tollens.