Sunk cost

Money or effort already spent that cannot be recovered regardless of future decisions. A common judgment failure is letting sunk cost (such as prior research investment) justify continuing a project rather than evaluating the project on its future dollar-denominated merits alone, as discussed in Question 4 of Section 10's knowledge check.

Money already spent that cannot be recovered whether you continue or stop. Sunk cost is a fact to learn from, not a reason to keep a value-destroying system alive; a forward-looking keep-or-kill decision counts only future benefits against future costs.

Money and effort already spent, which is gone regardless of what you do next and must therefore not influence a forward stop-or-continue decision. The correct question is always the best use of the next dollar, not what has already been committed.

Money, time, or effort already spent that cannot be recovered regardless of what you decide next. Because it is identical whether you continue or stop, it is irrelevant to any live decision; treating it as a reason to continue is the sunk cost fallacy.

Money and effort already spent, which is gone whether you continue or stop and therefore must not drive a forward decision; the adaptive-planning discipline is to weigh the next dollar's best use, not what is already spent.