Trade, also known as trading or exchange, was the activity of buying, selling, or exchanging of goods or services between individuals or species. Someone who engaged in this activity was called a trader.
Captain Christopher Pike asked the Talosians if some form of trade would save their species from eventual death. The Magistrate rejected the offer by explaining that the trade might result in Humans learning the Talosian power of illusion and destroying themselves too. (TOS: "The Cage")