Enthalpy

Enthalpy is the heat or energy content stored in a system. The chemical symbol representing enthalpy is H. Enthalpy can be lost or gained in a system, dependant on whether the overall reaction is exothermic or endothermic.

G.J. Van Wylen and R.E. Sonntag (1985), Fundamentals of Classical Thermodynamics, Section 5.5 (3rd edition), New York, NY, John Wiley & Sons Inc.