+A **sunk cost** is an expense already incurred and cannot be recovered. These past expenditures, often in [Time](/wiki/time) or [Money](/wiki/money), should not influence future choices. Rational decision-making focuses on current and prospective costs and benefits, ignoring what is already lost.
+## See also
+- [Decision Making](/wiki/decision_making)
+- [Cognitive Bias](/wiki/cognitive_bias)
+- [Opportunity Cost](/wiki/opportunity_cost)