The function of money that is NOT one of its primary functions is "double coincidence of wants."
Double coincidence of wants refers to the idea that in a barter system, for a trade to occur, both parties must have what the other wants and want what the other has. This can make trade difficult and inefficient.
Money, on the other hand, serves as a commonly accepted form of payment, making trade easier and more efficient by eliminating the need for a double coincidence of wants.
In summary, while double coincidence of wants is a concept related to barter systems, it is not a primary function of money. The primary functions of money are as a store of value, a medium of exchange, and a means of deferred payment.