Which of the following is a currency or a store of wealth of both?

* US dollar
* Gold
* Bitcoin

A currency is one that can be used as a medium of exchange. You can buy goods with a currency. The US dollar is a currency. It is difficult to use gold as a currency - except in a  crisis. It is also difficult to use Bitcoin as a currency because of the volatility in its price.

The US dollar was, at one time, also used as a store of wealth. Many national governments keep their reserves in US dollar.

However, this role is now being questioned. The US dollar is expected to lose its value. It is no longer suitable as a store of wealth.

Many people, including governments, now look towards gold and perhaps bitcoin as a store of wealth. They expect these assets to keep their value against a depreciating US dollar.

80% of international trade is now conducted with the US dollar. This role as a currency for international transaction may also diminish in the future. Its place could be taken over by other currencies, especially the Chinese yuan.