In chemical kinetics, the entropy of activation of a reaction is one of the two parameters (along with the enthalpy of activation) which are typically obtained from the temperature dependence of a reaction rate constant, when these data are analyzed using the Eyring equation of the transition state theory. The standard entropy of activation is symbolized  and equals the change in entropy when the reactants change from their initial state to the activated complex or transition state ( = change,  = entropy,  = activation).