An alliance of countries refers to a mutual agreement that two or more nations agree to cooperate with each other in various areas. However, there are various terms that can be used interchangeably with the phrase "alliance of countries". Some of the synonyms include a coalition of states, a confederacy of nations, an accord of nations, a federation of countries, a union of states, a bloc of nations, an association of sovereign states among others. These terms have slightly different meanings, but the underlying idea remains the same. They describe a group of nations that have come together to achieve a common goal, whether it is military, political, or economic. Alliances of countries continue to play a crucial role in global politics in the 21st century.