Money may be regarded as a conventional means of representing a claim or a right to goods or services. Its existence may result from everything on a scale between a tacit understanding within a society and state legislation. And a wide variety of objects may function as money in the different uses which this possesses—for payments, for storing wealth, for measuring value, and as a means of exchange. It is likely that at an early stage valuable and imperishable objects, such as metal, served to convert surplus produce into a means for the acquisition of other produce in the future; at the same time, any commodity, such as cattle, may have served for measuring value. A decisive step was taken when an organized community designated an official monetary unit, normally of precious metal, for collective purposes, whether for measuring value or for payments, for fines, or for taxes. This step had been taken in most near eastern kingdoms by the beginning of the iron age, in many Greek communities by 800 bce, in Rome by 500 bce. The production of money in the form of coinage began in western Asia Minor about 600 bce and spread rapidly in the Greek world, more slowly in the Phoenician world, in the Roman world from the late 4th cent. bce. In the Greek world, the use of spits, obeloi, as objects of value is reflected in the use of oboloi as monetary units and denominations of most Greek coinage systems. See coinage, Greek and Roman.
Despite the spread of coinage, not only in the Greek, Phoenician, and Roman worlds, but also to communities on their fringes—from Parthia to Spain—even in the high Roman empire, there were large areas of the Mediterranean world in which coinage played a minimal role; and many areas are likely at all times to have operated without any significant use of monetary institutions.
The ratio between the principal metals—gold, silver, bronze—varied over time, with such factors as the increasing transfer to the Greek world of gold from Persia or the exploitation of silver-mines in Spain; these shifts naturally affected the relationships between different monetary units and different coin denominations.
The Hellenistic period saw the development of systems of paper transfers of money, mostly in connection with the levy of taxes; and the Roman state was able to a limited extent to function on anticipated revenues. But the ancient world never developed any form of paper money, and (despite Harris) only limited use of credit mechanisms to increase the money supply.