exotherm

This term is used primarily within the specialized registers of chemistry and thermodynamics. It describes a process where the enthalpy of the products is lower than that of the reactants, resulting in the emission of heat into the surrounding environment.

While "exothermic" is the far more common adjective used to describe such reactions, "exotherm" serves as the noun to categorize the process itself. It is a technical term and is rarely encountered in casual conversation or general literature.