A single currency is a coin or paper money system that is used as a common tender or currency across a geographic region such as a country, a group of countries or continents. Some synonyms for a single currency include monetary union, unified currency, common currency, shared currency, or integrated currency. Another popular term used in the European Union is the Euro, which represents the shared currency of 19 countries. This single currency system has allowed for easier trade, investment and economic cooperation among the participating countries. Furthermore, many countries are also considering the adoption of a single currency to enhance economic growth, investment and trade opportunities.