An exchange rate (also known as a foreign-exchange rate) between two currencies is the rate at which one currency will be exchanged for another. It is also regarded as the value of one country's currency in terms of another currency.
Exchange rates are determined in the foreign exchange market, which is open to a wide range of different types of buyers and sellers and where currency trading is continuous: 24 hours a day except weekends (from 20:15 GMT on Sunday until 22:00 GMT on Friday). The spot exchange rate refers to the current exchange rate. The forward exchange rate refers to an exchange rate that is quoted and traded today, but for delivery and payment on a specific future date.
Since the beginning of 2019, the dollar has lost 0.9% of its value against the Japanese yen. There still exists a demand elsewhere for safe haven assets, Japan just seems to have fewer concerns about global growth than the rest of the world. Also, expectations of a less steady interest rate increase at the Federal Reserve have caused a slight decrease in demand for the dollar in Asia.
The mixed bag being the dollar versus the European exchanges: for GBP/USD the pound sterling is up roughly 4.0% YTD. The EUR/USD is currently about 2.3% lower for 2019.
The ICE U.S. Dollar index, a gauge of the dollar's value against a basket of six currencies, is 0.4% since the beginning of 2019 and as of December 31 stands at 96.45.
The U.S. Dollar Index is a weighted geometric mean of the dollar's value relative to the following select currencies and their corresponding weight: EUR (57.6%), JPY (13.6%), GBP (11.9%), CAD (9.1%), SEK (4.2%) and the Swiss Franc, CHF (3.6%).