Trade is the exchange of goods or services among two or more parties. In its original form trade had to be negotiated through barter and the exchange of goods and services of a recognized equal value that was wanted by both parties. Modern trade is generally negotiated through the use of a medium of exchange, i.e. money, and rarely through barter: as a result one can separate buying and earning or selling. The invention of money greatly simplified and promoted the development of trade.
See also: International trade, Trade bloc, Globalisation, Business, Retail.