Tenkan vs Tenkai

A question came up the other today about the difference between the words "tenkan" and "tenkai" which I think gets confused at times. As far as I understand it... Tenkan 転換 breaks down as: 転 suddenly, quickly 換 change, alter, substitute and together 転換 as convert or divert You might think of it as changing direction suddenly, or diverting uke's energy. In aikido, it refers to a turning movement (tenkan ashi), usually 180 degrees: Tenkai 転回, however, breaks down like this: 転 suddenly, quickly 回 turn, rotate, revolve and together 転回 as revolution or rotation In much of the aikido world, it refers to a form of movement, what we commonly call a "hip switch", where you turn 180 degrees but without moving our feet (we do it in the Walking Kata, but there it's called "ude goshi gaeshi" or arm-hip reversal, which frankly is probably more clear): Both tenkan and tenkai are part of what's called tai sabaki or ...