Thermodynamic System: This refers to a portion of the universe under study where changes occur. It can be an open system (exchanges energy and matter with surroundings), closed system (exchanges only energy), or isolated system (no exchange).
Entropy: Entropy is a thermodynamic quantity representing the unavailability of a system's thermal energy for conversion into mechanical work, often interpreted as the degree of disorder or randomness in the system.
Enthalpy: Enthalpy is another state function that describes heat content within a reaction/system at constant pressure.