The value of currency of a country is expressed in terms of US Dollar. The US Dollar is the most widely accepted and dominant currency in the world. It serves as the primary reserve currency and is used for international transactions and trade.

The US Dollar as a Reserve Currency:
- The US Dollar has been the dominant reserve currency since the end of World War II. Many countries hold US Dollars as part of their foreign exchange reserves to facilitate international trade and stabilize their economies.
- The US Dollar's status as a reserve currency is supported by the economic and political stability of the United States, as well as the size and liquidity of its financial markets.
- The US Dollar's reserve currency status also stems from the fact that the United States is the world's largest economy and has a strong influence on global trade and financial systems.

Factors Influencing the Value of Currency:
- The value of a currency is determined by various factors, including supply and demand dynamics, interest rates, inflation, economic growth, geopolitical factors, and market sentiment.
- Currency exchange rates fluctuate based on these factors, and the value of a currency relative to another currency is determined by the foreign exchange market.
- In the case of expressing the value of a currency in terms of US Dollars, the exchange rate between the two currencies is used to calculate the value.

Importance of Expressing Currency Value in US Dollars:
- The US Dollar's dominant position in the global economy makes it the standard currency for expressing the value of other currencies.
- Expressing currency value in US Dollars provides a common benchmark for comparison and facilitates international trade and investment.
- It allows businesses and individuals to easily understand the value of different currencies and make informed decisions regarding foreign exchange transactions.

Conclusion:
In conclusion, the value of a country's currency is generally expressed in terms of US Dollars due to its status as the dominant reserve currency and its widespread use in international trade and finance. The US Dollar's stability, liquidity, and influence on global economic systems make it the preferred currency for expressing the value of other currencies.