An approximation used in quantum mechanics when the time dependence of parameters, such as the internuclear distance between atoms in a molecule, is slowly varying. This approximation means that the solution of the Schrodinger equation at one time goes continuously over to the solution at a later time. It was formulated by Max Born and the Soviet physicist Vladimir Alexandrovich Fock (1898-1974) in 1928. The "Born-Oppenheimer approximation is an example of the adiabatic approximation.