Isoenthalpic is a term often used in thermodynamics to describe a process that occurs at constant enthalpy. However, there are several synonyms for this word, including isoenergetic, isentropic, adiabatic, and isothermal. Isoenergetic refers to a process that occurs at constant energy, while isentropic describes a process that occurs at constant entropy. Adiabatic refers to a process where no heat is exchanged with the surroundings, and isothermal refers to a process that occurs at constant temperature. While each of these words has a slightly different meaning, they all define processes that occur under specific conditions where particular values remain constant.