In chemical kinetics, the hypothetical state that is mid-way between reactants and products, poised at a point where the reaction is as likely to go forward to products as it is to fall back to reactants. If the reactants and transition state may be considered to be in equilibrium, application of the second law of thermodynamics allows analysis of the temperature-dependence of reaction rates. The concept may be applied to enzyme kinetics to describe the transition from enzyme–substrate complex to enzyme–product complex.