Adam Smith is widely regarded as the father of economics due to his seminal work, "The Wealth of Nations", which laid the foundation for classical economics.

Classical economics, particularly the theories of Adam Smith and David Ricardo, places a strong emphasis on the forces of supply and demand in determining prices.

Karl Marx's theory of surplus value argues that the value of a commodity is determined by the amount of labor required to produce it, and that the capitalist class extracts surplus value from workers by paying them less than the value of their labor.

John Maynard Keynes's theory of effective demand emphasizes the importance of aggregate demand in determining economic output and employment.

Monetarism, as advocated by Milton Friedman, focuses on the role of money supply in influencing economic activity and inflation.

The concept of diminishing marginal utility is a fundamental principle in neoclassical economics, which suggests that as more units of a good or service are consumed, the additional satisfaction derived from each additional unit decreases.

Keynesian economics, particularly the work of John Maynard Keynes, highlights the role of expectations and animal spirits in influencing economic behavior and decision-making.

The concept of rational expectations in economic theory assumes that individuals make decisions based on available information and rationally update their expectations as new information becomes available.

Institutional economics, as pioneered by Thorstein Veblen and John R. Commons, focuses on the role of institutions and social norms in shaping economic behavior and outcomes.

Behavioral economics explores the influence of emotions, cognitive biases, and psychological factors on economic decision-making.

Endogenous growth theory, as developed by Robert Lucas and Paul Romer, highlights the role of technological change and innovation as key drivers of economic growth.

Game theory in economics analyzes the behavior of individuals and groups in strategic situations, where the actions of one player affect the outcomes for others.

Information economics, pioneered by George Akerlof, Michael Spence, and Joseph Stiglitz, explores the impact of information asymmetry and moral hazard on economic transactions and outcomes.

The concept of externalities in economics refers to the costs or benefits of economic activities that are not reflected in market prices, leading to market failures.

Welfare economics focuses on the analysis of social welfare and equity in economic outcomes, aiming to maximize the overall well-being of society.