	An input-consuming logic gate "L" is reversible if, for any output "y", there is a unique input "x" such that applying "L"("x") = "y". If a gate "L" is reversible, there is an inverse gate "L"′, which maps "y" to "x" for which "L"′("y") = "x". From common logic gates, NOT is reversible, as can be seen from its truth table below.