Comparative Advantage
the ability of a party (an individual, a firm, or a country) to produce a particular good or service at a lower opportunity cost than another party. It is the ability to produce a product most efficiently given all the other products that could be produced.
Externality
an impact on a party that is not directly involved in the transaction. In such a case, prices do not reflect the full costs or benefits in production or consumption of a product or service.
Marginal
the utility gained (or lost) from an increase (or decrease) in the amount available of that good or service.
Market
In mainstream economics, the concept of a market is any structure that allows buyers and sellers to exchange any type of goods, services and information.
Scarcity
the fundamental economic problem of having seemingly unlimited human needs and wants, in a world of limited resources.