Sunk Cost: A sunk cost is an expense that has already been incurred and cannot be recovered. Sunk costs should not be considered when making future decisions, as they are irrelevant to the current choice at hand.
Marginal Analysis: Marginal analysis is the examination of the additional benefits and costs associated with one more unit of an activity. It helps decision-makers evaluate the trade-offs and opportunity costs of incremental changes.
Economic Efficiency: Economic efficiency refers to the optimal use of limited resources to maximize the production of goods and services. Opportunity cost is a key concept in achieving economic efficiency, as it guides the allocation of resources to their most valuable uses.