Currency pair euro has strengthened, or both. On the other hand, if the EUR/USD (or EURUSD) quote changes from 1.2500 to 1.2490 the euro has become relatively weaker than the dollar. The rules for formulating standard currency pair notations result from accepted priorities attributed to each currency. From its inception in 1999 and as stipulated by the European Central Bank, the euro has first precedence as a base currency. Therefore, all currency pairs involving it should use it as their base, listed first. For example, the US dollar and euro exchange rate is identified as EUR/USD. Although there is no standards-setting body
De facto currency De facto currency A de facto currency is a unit of money that is not legal tender in a country but is treated as such by most of the populace. The United States dollar and the European Union euro are the most common de facto currencies. Andorra used the euro unofficially prior to June 2013, at which point the euro became its official currency. The euro remains the de facto currency in Kosovo and Montenegro. Countries using the United States dollar as their de facto currency include Aruba and Cambodia, where most hotels, restaurants, and transportation are priced in dollars;