A physical constant that is a measure of the strength of interaction between two parts of a system or two or more systems. In the case of a field theory, the coupling constant is a measure of the magnitude of the force exerted on a particle by a field. In the case of a quantum field theory, a coupling constant is not constant but is a function of energy, the dependence on energy being described by the renormalization group. See also coupling; fine structure; asymptotic freedom.
Subjects: Physics — Chemistry.