Triangular trade was supposedly a trans-Atlantic British trade route that had three parts or "sides" to the "triangle": Africa to the Americas to transport slaves, the Americas to Europe to transport raw materials, and Europe to Africa to transport finished goods for sale.
It was developed by the Portuguese in the 16th century, but later used by Britain, France, Holland, Colonial America and the other maritime nations of Europe.
It is disputed whether trade really occurred in a "triangle", and there are good reasons to be skeptical. For example, there was no significant market in Africa for finished goods. The term "triangular trade" itself was not used contemporaneous with the trade.
- Ostrander, Gilman M. "The Making of the Triangular Trade Myth", William and Mary Quarterly, 30 (1973), 635-44. in JSTOR