In chemistry, bond-dissociation energy (BDE) or D₀, is one measure of the strength in a chemical bond. It can be defined as the standard enthalpy change when a bond is cleaved by homolysis, with reactants and products of the homolysis reaction at 0 K (absolute zero). For instance, the bond-dissociation energy for one of the C–H bonds in ethane (C₂H₆) is defined by the process:
CH₃CH₂–H → CH₃CH₂· + H·