三个世界
As political science, the Three Worlds Theory is a Maoist interpretation and geopolitical reformulation of international relations, which is different from the Three-World Model, created by the demographer Alfred Sauvy in which the First World comprises the United States, the United Kingdom, and their allies; the Second World comprises the Soviet Union, the People's Republic of China, and their allies; and the Third World comprises the economically-underdeveloped countries and the countries, including the 120 countries of the Non-Aligned Movement (NAM).