The linear relation between energy of activation Ea and enthalpy of reaction ΔHr sometimes observed within a series of closely related reactions. \[E_{\text{a}} = A + B\ \unicode[Times]{x394}H_{\text{r}}\]
Source:
PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1088 (https://doi.org/10.1351/pac199466051077)