The study of the properties of motion that are independent of the nature of the forces. In reaction dynamics the term is often applied in particular to effects that occur when atomic masses are changed, the forces remaining the same.
Source:
PAC, 1996, 68, 149. 'A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)' on page 170 (https://doi.org/10.1351/pac199668010149)