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state functions refer to the minimum set of properties that decribes the state of a system. eg. pressure, volume, temperature all are state function. state functions are unique in the sense their values are independent of the process that act on the system. no particular fixed process is required to achieve a certain set of state functions. most importantly, state functions always describe the state of the system. if you a mixture of 3 gases, their molar composition would also be a state function.