People often use the term “Third World” as shorthand for poor or developing nations. By contrast, wealthier countries such as the United States and the nations of Western Europe are described as being part of the “First World.” Where did these distinctions come from, and why do we rarely hear about the “Second World?”

The “three worlds” model of geopolitics first arose in the mid-20th century as a way of mapping the various players in the Cold War. The origins of the concept are complex, but historians usually credit it to the French demographer Alfred Sauvy, who coined the term “Third World” in a 1952 article entitled “Three Worlds, One Planet.” In this original context, the First World included the United States and its capitalist allies in places such as Western Europe, Japan and Australia. The Second World consisted of the communist Soviet Union and its Eastern European satellites. The Third World, meanwhile, encompassed all the other countries that were not actively aligned with either side in the Cold War. These were often impoverished former European colonies, and included nearly all the nations of Africa, the Middle East, Latin America and Asia.

Today, the powerful economies of the West are still sometimes described as “First World,” but the term “Second World” has become largely obsolete following the collapse of the Soviet Union. “Third World” remains the most common of the original designations, but its meaning has changed from “non-aligned” and become more of a blanket term for the developing world. Since it’s partially a relic of the Cold War, many modern academics consider the “Third World” label to be outdated. Terms such as “developing countries” and “low and lower-middle-income countries” are now often used in its place.