Medium of Exchange.....

Medium of exchange is a term in man-made economics referring to any designated material object which invariably is used by one human being to acquire a necessary or desired good or service from another..... The underlying assumption in designating a "medium of exchange" is that one cannot acquire a good or service from another, without having to provide the other with something material in exchange.

The origin of "mediums of exchange" in human societies is nearly universal in the 21st century, and is assumed to have arisen in antiquity as awareness grew of the limitations of barter. The form of the "medium of exchange" has assumed that of a token, which has been further refined as money. A "medium of exchange" is in fact considered one of mankind's three fundamental functions of money, according to mainstream rules of economics. Because it can be to acquire any good or service it acts as an intermediary instrument and avoids the limitations of barter; where what one wants has to be exactly matched with what the other has to offer.

Most forms of money are now recognized as mediums of exchange including commodity money, representative money, the new cryptocurrency and most commonly fiat money. Representative and fiat money often exist in digital form as well as physical tokens such as coins and notes.