means The branch of science concerned with the rates at which processes happen and the forces or steps that drive them — most often the study of how quickly chemical reactions proceed.

from From Greek kinētikos, 'of motion,' which comes from kinein, 'to move' — the same restless root behind 'cinema' (literally moving pictures) and 'kinetic.' The word entered scientific English in the 19th century as physicists and chemists carved out the study of things in motion, whether bodies or molecules.