Is dollar the U.S. dollar?
The word "dollar" has become synonymous with "US dollar" in daily life, but strictly speaking, the two are not completely equivalent. The U.S. dollar is the currency unit of the United States, and the U.S. dollar generally refers to currencies denominated in U.S. dollars. Therefore, when we say "USD", we refer to the currency of the United States; and when we say "USD", it may include other currencies denominated in US dollars, such as Singapore dollars, Hong Kong dollars, etc.