Triangular trade, or triangle trade, is a historical term indicating trade among three ports or regions. The trade evolved where a region had an export commodity that was required in the region from which its major imports came. Triangular trade thus provided a mechanism for rectifying trade imbalances.
The most famous triangle trade in human history was the 18th century trade among Europe, West Africa, and the West Indies and North American colonies.  (alternatively: West Africa, the West Indies, and northern colonies in British North America). Of these, the sea lane west from Africa was the notorious Middle Passage; its cargo, abducted or recently purchased African slaves
Other triangular trades
The term “triangular trade” also refer to a variety of other trades:
• A trade pattern which evolved before the American Revolutionary War between Great Britain, the colonies of British North America, and British colonies in the Caribbean. This typically involved exporting raw resources such as fish (especially salt cod) or agricultural produce from British North American colonies to feed slaves and planters in the West Indies (also lumber); sugar and molasses from the Caribbean; and various manufactured commodities from Great Britain.
• The shipment of Newfoundland salt cod and corn from Boston, Massachusetts in British vessels to southern Europe.
• The “sugar triangle” whereby American ships took local produce to Cuba, then brought sugar or coffee from Cuba to St Petersburg, then bar iron and hemp back to New England.