In fact, the definition of international currency is freely convertible foreign exchange generally accepted by the international community. Like the euro, it belongs to the international currency.

The United States established its dominant position mainly by the international monetary system established after World War II. This monetary system is called the Bretton Woods system, and the US dollar was determined as the reserve currency of all countries at that time, which made the US dollar widely circulated around the world. Although the system collapsed in the 1970 s, it did not change people's habit of using US dollars for settlement.