Co-ordinates and “vibrationally-adiabatic” approximations are described for reactions in three dimensions. Some reactions may demonstrate a fairly strict adiabaticity for certain degrees of freedom and a statistical adiabaticity for others. Some will simply be strongly vibrationally-nonadiabatic. Several topics in kinetics are considered from the viewpoint of vibrational-adiabaticity or mild non-adiabaticity.