river bed (river beds plural) , riverbed A river bed is the ground which a river flows over. n-count. up-river, upriver. Something that is moving up-river is moving towards the source of a river, from a point down the river.
In economics, the term trade-off is often expressed as an opportunity cost, which is the most preferred possible alternative. A trade-off involves a sacrifice that must be made to get a certain product or experience. A person gives up the opportunity to buy 'good B,' because they want to buy 'good A' instead.
Trade is the concept of exchanging goods and services between two people or entities. International trade is then the concept of this exchange between people or entities in two different countries. People or entities trade because they believe that they benefit from the exchange.