The definition of money is a medium of exchange. Not only in paper form but also in metal form depending on which countries agree on the form and type of their money.
In my country, money is known as Rupiah (Rp). With Rupiah we can spend anything we want using Rupiah because Rupiah is a legal means of payment.
I think it's the same in other countries too.
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That's not correct!
Currency is not ANYTHING used as a medium of exchange, you can use many things as a medium of exchange which I'm sure is obvious around you. You can purchase your shoe and other products and properties with gold or other products and properties, which makes your definition faulty.
If this is what causes the definition of money to be wrong in your opinion because gold can also buy products or property, I think you are trying to play the function of reason.
Before fiat was in the form of paper or metal, perhaps the ancient Egyptians [Pharaoh] also had a different definition of money.
The legal means of payment determined by the state are fiat currencies such as USD, Rupiah, Euro, Rubber, Yuan, Yen and so on. However, if the exchange or bartering depends on both parties, if you want to barter with a friend regarding goods or services, that is also legal (for example, bartering gold and shoes or gold with other collectibles or collectibles with collectibles). However, when it comes to legal payments, the only thing that is determined by the state is to use the fiat currency of each country.
Before the fiat currency system was in operation, the coins used were gold and silver or a barter system was used.