Convenience Yield
The benefit or premium associated with holding an underlying product or physical good, rather than the contract or derivative product.
Investopedia Commentary
Sometimes, due to irregular market movements such as an inverted market, the holding of an underlying good or security may become more profitable than owning the contract or derivative instrument, due to its relative scarcity versus high demand.
An example would be purchasing physical bales of wheat rather than future contracts. Should their be a sudden drought and the demand for wheat increases, the difference between the first purchase price of the wheat versus the price after the shock would be the convenience yield.
See also: Backwardation, Commodity, Contango, Demand, Derivative, Futures, Futures Contract, Inverted Market, Underlying