Real Dictionary

commerce
uncountable noun: Commerce is the activities and procedures involved in buying and selling things.

commerce in American English
the buying and selling of goods, esp. when done on a large scale between cities, states, or countries; trade
to have personal dealings (with)
noun: an interchange of goods or commodities, esp. on a large scale between different countries ( foreign commerce) or between different parts of the same country ( domestic commerce); trade; business

commerce in British English
noun: the activity embracing all forms of the purchase and sale of goods and services