Middle-income countries refer to nations that have a moderate level of economic development, falling between low-income and high-income countries. These countries typically have a GDP per capita between $1,000 and $12,000, as defined by the World Bank. Middle-income countries face unique challenges in terms of economic growth, social development, and governance. Research in this area may focus on strategies for sustainable development, poverty reduction, and addressing income inequality. Additionally, researchers may explore the impact of globalization, trade policies, and technology on middle-income countries. Studies may also examine the role of international organizations, foreign aid, and domestic policies in promoting growth and development in these nations.