In thermodynamics, the term exothermic ("outside heating") describes a process or reaction that releases energy usually in the form of heat, but also in form of light (for example a spark, flame, or explosion), electricity (for example a battery), or sound. Its etymology stems from the Greek prefix ex- (meaning "outside") and the Greek word thermein (meaning "to heat"). The term exothermic was first coined by Marcellin Berthelot. The opposite of an exothermic process's an endothermic process, o… (More on Exothermic)