Scarcity, the fundamental economic problem, shapes how individuals and societies make decisions. With limited resources and unlimited wants, we're forced to choose between alternatives, each with its own opportunity cost. This unit explores these concepts and their real-world applications. The Production Possibilities Frontier (PPF) illustrates scarcity, choice, and opportunity cost graphically. We'll examine how marginal analysis helps in making optimal decisions and apply these ideas to personal finance, business, and government policy.