Marketing is the study and management of exchange relationships. Marketing is used to create, keep and satisfy the customer. With the customer as the focus of its activities, it can be concluded that Marketing is one of the premier components of Business Management - the other being innovation.
Trade involves the transfer of goods or services from one person or entity to another, often in exchange for money. A system or network that allows trade is called a market.
When a general usage has been judicially ascertained and established, it becomes a part of the law merchant, which Courts of justice are bound to know and recognise.
Lord Campbell, Brandao v. Barnett (1846), 12 CI. & F. 805.