1. Homogeneous Goods
Two goods are called homogeneous for a consumer if the consumer would always be willing to give up one unit of one good for one more unit of the other good, and keep his utility fixed. Homogeneous is a special case of perfect substitutes which, in turn, is a special case of substitutes.
2. Bandwagon Effect
The bandwagon effect is a positive network externality in that a consumer's demand for a good increases with the number of other consumers who have purchased the good.
3. Consumer surplus
Consumer surplus is the difference between the maximum amount a consumer is willing to spend on a good and the amount that the consumer actually spent on the good at the market price.
4. Idle time
The cost of direct labour for employees unable to perform their assigned tasks because of machine breakdowns, shortage of materials, power failure, sloppy production scheduling, and the like. The cost of idle time is treated as part of factory overhead that is, as part of indirect manufacturing costs that should be spread over all the production of a period.