Opportunity Cost

Opportunity cost is one way to measure the cost of something. Rather than identifying and adding the costs of a project, one may also identify the next best alternative way to spend the same amount of money. Giving up the profit of the next best alternative is the opportunity cost of the original choice. Opportunity cost is not the sum of the available alternatives, but rather the benefit, of the single best alternative. Unless otherwise specified, when economists say "cost", they are referring to opportunity cost.