trade , noun:

1 [mass noun] the action of buying and selling goods and services:a move to ban all trade in ivorya significant increase in foreign trade;
2 a job requiring manual skills and special training:the fundamentals of the construction trade[mass noun] :he's a carpenter by trade;
3 (the trade) [treated as singular or plural] the people engaged in a particular area of business:in the trade this sort of computer is called ‘a client-based system';

commerce, noun:

1 the activity of buying and selling , especially on a large scale:the changes in taxation are of benefit to commerce;
2 dated social dealings between people:the noise and warmth of human commerce.