The first world, the second world and the third world roughly divide the countries in the world into three categories. These three words will not appear at the same time. After World War II, people often regard the members of the North Atlantic Treaty Organization and Warsaw Treaty Organization as two types of countries, and regard the free world and the Soviet bloc as one. At this time, there is no concept of the first and second "world". People soon realized that there are still many countries that do not belong to these two categories. In the 1950s, they were mentioned by the Third World. Thus, there is the first world and the second world.

Finally, the countries in western Europe and the countries under the "influence" of the United States are regarded as the first world. In addition to North America and Western Europe, the first world countries also include other industrialized capitalist countries, such as Japan and former British colonial countries, such as Australia, New Zealand and South Africa.

There are still some countries that do not fully meet the definition of the first world, such as Switzerland, Sweden, Ireland and the United States. These countries are neutral countries. Finland is influenced by the Soviet Union, but it is not a producer or a member of the Warsaw Pact. Austria was influenced by the United States, but became a completely independent republic in 1955. So it is neutral. Turkey joined the North Atlantic Treaty Organization on 1952, but it is not an industrialized country and is not completely located in Western Europe. Spain did not join the North Atlantic Treaty Organization until 1982, when the cold war ended and dictator Franco died. 199 1 after the disintegration of the Soviet union, the saying of the second world gradually withdrew from the historical stage. At the same time, the first world began to include all developed countries.

In addition, China leader Mao Zedong put forward in 1974: "I think the United States and the Soviet Union are the first world. Middle school, Japan, Europe, Canada, the second world. We are the third world. " "The third world has a large population. Apart from Japan, Asia is the third world. All of Africa is the third world, and Latin America is the third world. "

Later, Deng Xiaoping further elaborated at the UN General Assembly: "From the perspective of changes in international relations, there are actually three interrelated and contradictory aspects and three worlds in the world today. America and the Soviet Union are the first world. Developing countries in Asia, Africa and Latin America are the third world. The developed countries in between are the second world. "

This definition is very popular in China literature (especially in Chinese mainland).

In recent years, many developing countries have also achieved industrialization, and the term "fourth world" has begun to appear, referring to those countries that do not belong to global economic integration and lack the basis of industrialization.