Equilibrium is a state in which the system's properties, such as temperature, pressure, and concentration, remain constant over time. At equilibrium, the rates of forward and reverse reactions are equal, and there is no net change in the system's composition.

In thermodynamics, work (w) is defined as the transfer of energy from one system to another through a force applied over a distance. It is a measure of the energy expended or gained by a system as it changes its state. Work can be done on or by a system, and it is typically denoted by the symbol "w".

Free energy (G) is a thermodynamic property that describes the energy available to do work in a system at constant temperature and pressure. It is a measure of the maximum amount of work that can be done by a system as it changes its state from one equilibrium state to another. Free energy is related to the system's energy and entropy.